7 radi december, -...

.

RADI AND

IN AUSTRALIA

Uol. 7 No. 9

DECEMBER, 1945

Registered a+ the G.P.O.. Sydney. for transmission by

post es e periodical.

BUILDING AN AUTO RECEIVER

1

Island Radio and Broadcast Stations.

. . . Are in charge of Aeradio and Ship Stations.

. . Maintain Ambulance, Police and other mobile Radio Services.

MARCONI SCHOOL OF WIRELESS CONDUCTED BY AMALGAMATED WIRELESS (A/SIA) LTD.

47 YORK ST., SYDNEY - 163 QUEEN ST., 'MELBOURNE ' Tel. B 0522 Tel.: M 4161

, I

AERADIO STATIONS e;?

j hCl !s

COASTAL RADIO

PAGE II. RADIO AND HOBBIES IN AUSTRALIA DECEMBER, 1945

THE KEY TO A StaressiaLareer in aâca

MARCONI SCHOOL GRADUATES HOLD THE BEST POSITIONS IN

AUSTRALIAN RADIO

They . .

are employed in Radio Development and Research Laboratories.

... Staff A.W.A. Beam Wireless Stations.

. . Operate all A.W.A. (`.natal RtIAL,

To -days demand for Qualified Wireless Operators and Broadcast Technicians far exceeds the supply.

i'.; -i: RESEARCH

RADIO IN

AND WOB B I ES AUSTRALIA

going- 2)own EGVERY substantial extension in the

frequency range of audio equipment is likely to Introduce compli- cations, which may prompt the question: "Is it worth while?" An increased treble response may discover unsus- pected sources of harmonie distortion, while extension in the bass register has its own likely effects.

Our recent work with tone -control stages, cathode loading and extensive negative feedback has brought many letters of commendation; but others report Indifferent success. This was not unexpected. For the first time many readers are possessed of amplifiers in which 30 -cycle vibrations- spurious or othervbise-are not substantially t.bliterated by reactive losses.

Some have found that their time-honored turntable has a low frequency rumble. Others have struck trouble with cabinet feedback from the loudspeaker to the pickup. These troubles are mechanical in origin and require like treatment.

The increased efficiency below 60 odd cycles is liable to increase cone and cabinet resonance effects, with some -loudspeaker systems. We have a few fresh ideas about baffling, which should meet this situation, however.

Electrical d'fficulties have sometimes followed the incor- poration of a tone -control stage or parallel output system in an existing set. The equipment "motor -boats" slowly with the bass control advanced.

This again, is not negligent design on our part. The circuit arrangements in question may each increase the 30 -cycle response by 12 or more decibels, and a total boost of 25 db in the bass requires more than usual care with decoupling. Some tuners, for example. may have to be supplied through a separate resistance filter, direct from the rectifier filament. /

The fidelity "baby" has / // t!// heel nlenfv of teething / I_/

Mc GILL'S RADIO COLUMN

Price Post Mills-Radio Technique .. .. 0/8 .. 441

Huag-Basic Radio .. .. . 33/3 .. 64 R.C.A. Receiving Tube Menuai 2/0 .. ad R.C.A. - Transmitting Tube

Manual .. .. .. .. .. .. . 2/4 .. 3d Radlulron->esigncrs Handbook 6/- Seruggie-Faundatlona of Wire-

less 10/8 .. ad Dunlop and Haan - Electrical

and Radio Dictionary 7/8 .. ad B.S.I.-Glossary of Terms Used

In Teleoommunlcation 6/9 .. ad Putliek - Television Without

Beatty-Radio Data Charts . 12/- .. 6d Flood-Elementary Principles

of Wireless .. .. .. .. 2/5 .. Sd Longmsn'e-Wireless and How

.. 1/8 .. 2d Flo d - Elementary Eltctrlolty

for Radio Students 1/9 .. 26 H.M.S.O.-Electricai and Radio

Notes for Wireless Operator. 6/2 .. 4d Crook-Elementary Handbook

for Wireless Operators . . 8/9 .. 4d Audels-Radioman's Guide, in-

cluding Electronics and Tele- vision .. .. .. .. .. .. .. 33/- .. 64

Admiralty-Handbook of Wire- less Telegraphy - 2 Volumes cotnnlete .. .. .. .. .. .. 11/8 .. lid

A.R.! - Radio Amateurs' Handbook. 1045 . . 11 /6 .. 94

A.R.R.L.-A Course In Radio Fundamentals . 5/- . S4

A.R.R.L.-Antenna Handbook 4/8 .. 3d English Edition-Amateur Radio

Handbook //- .. ad English Edillon-Radio Hand-

book Supplement . .. .. 4/5 .. 3d Gernebock - Television 104 2Vni. Amstrad and Tuthill - Radio

Material Guide Squire - Classified Radio Re-

ceiver Diagrams . 16/2 .. ad Camm-The Superbet Manual 7/9 .. ad Carom-Practical Wireless Cir-

culi. .. Carom-Wireless Transmission 7/9 .. 94 "Decibel"-Wireless Tererm. Ex-

plained .. .. .. .. . 4/10.. ad "Decibel" - Flni Course In Wireless 7/11.. ad Stranger-Dictionary of Radio and Television Terms 7/6 ,. 44 Stranger - Outline of Wireless 17/6 .. 66 Stranger-Mathematics of Wire- less

Revner-Cathode-Ray Oseillo-

Revnel-Radi, Communication, Volume 1 . 11/4 .. 4d Revner-Radio Communication, Volume 2 ..

Jones-Radio Handbook . 15/- .. 9d Ramo and lVhinnery - Fields and Waves In Modern Radio 35/- , ad rrrman - Radio Engineers'

MAGAZINES 'BY ANNUAL üBSOR1PTION

troubles and there are pro-- b ably a lot more ahead.

INDEX Page Page

"X" Marks The Spot For Invasion . 3 Pentodes And Beam Power Tetrodes 28 Snatched Aloft By A Speeding Plane 4 Trade Notes And New Releases 31 Machines Know All The Answers 5 A Reader Built It .. 32 A Story About Artificial Rock .. .. 6 Broadcast Band DX .. .. .. 34 Jap Plane Designers Tried Hard .. 9

Short -Wave Notes .. . . 35 Build This Simple Flying Model Science On the March .. .. .. How To Build An Auto Receiver Introduction To UHF Technique .. A Course In Radio Transmitters

IO 13

15

21

.. This Month's Recordings Skittles-Without The Backache Safe Keeps Food Cool .. .. .. Technical Book Review _- .. ..

39

40 41

42 (Part I) -- . .. .. .. .. 24 Answers To Correspondents .. 43

Radio, 1/8/-- Q.S.1., £1: Radio Craft. £ 1/2/-; Communications, £ 1/ei-: Service. £1/3/-: C.Q. Amateur Radio Magazine, £ i/:/6: Popular Science, £ 1/3!6; Popular Mechanics. £ 1/3/6: Science and Mech- anics. 6/-: Scientific American, £ 1/16/-; American Photography. £ 1/6/-: U.S. Cam -I era, l6-; Camera, £1/9/-; American Cinematographer, £ 1/4/.; International Projectionist, £ 1; Moyle Makers. £ 1121-: Society Motion Picture Engineers, £3/4/ - Add exchange to Cheques.

l McGILL'S AGENCY

(Est. 1860) (The G.P.O. is opp.)

183-185 ELIZABETH STREET, MELBOURNE.

PUBLISHED BY ASSOCIATED NEWSPAPERS LTD., at 60-70 ELIZABETH -ST, SYDNEY.. Phone BO333. Box 2728C, GPO, Sydney.

ADVERTISEMENT

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BUY A WAR ROND TODAY!

PAGE TWO RADIO AND HOBBIES FOR DECEMBER, 1945

FEATURE STORY

"X"MARKS THE SPOT FORiNVASION.. On the pitch-black night on June 6, 1944, paratroops and gliders opened the invasion of Nazi Europe. That they come down within yards of the appointed landing zones was no stroke of luck-it was yet another triumph for Radar. Here is the story of "Rebecca" and "Eureka," two mighty midgets.

Malcolm Goldfinch (Ex-R.A.A.F., Exclusive to "Radio and

THE air -borne forces in Britain were the Cinderellas of the

RAF till Churchill decided that they would form the spearhead of invasion.

At the beginning of 1944 the squadrons, which had been receiving only equipment not wanted by the other Commands and the Tactical Air Force, were given No. 1 priority and the number of squadrons trebled.

Previously, just a few squadrons. equipped with Whitleys. Halifaxes and Albermarles, had been laboriously carrying out experimental exercises, testing new equipment and new tac- tics for paratroop -dropping and glider - towing. Bomber Command gave up the Stirling and a number of these huge machines were modified for airborne operations.

During the testing period the "Back - room Boys" had not been Idle, and two Radar sets, "Rebecca" and "Eureka," had been developed and perfected. These sets were almost exclusive to airborne forces and their operational aircraft were fitted with the "Rebecca" set and navigators trained in its use.

AIRBORNE TECHNIQUE Towards the end of 1943, Bomber

Command had enough "G" Radar sets, and these, too, became available to the airborne squadrons.

To understand the use of "Rebecca" and "Eureka," it Is

necessary to know something of the technique of airborne operations. The tactical commander selects an

Hobbies")

GRIL

C FOCUS RANGE

1 1 1??-IS,,I.

Illustrating the nature of the signal visible on the screen of the

"Rebecca" set in the aircraft.

Force crews. A small body of men, dropped away from the main body, would be wiped out in a short time.

The aircraft have to fly at 600 feet to make a compact drop, and so that the paratrooper is only in the air for the minimum time. The crews of the planes are often briefed to drop within seconds of each other.

In order to facilitate all this and help the planes find the actual field en which the men have to be dropped, they first fly to what is known as a "rendezvous," which would be a pro- minent land- mark. T h e pilot and navigator have to bring the aircraft over this point, dead on

height gradually, reduce speed, open the bomb -doors, continually alter direction and gain or lose speed, so that he arrives right on time over the DZ. Meanwhile, the paratroops are moving towards the dropping hole and altering the trim.

Just' before the moment of dropping, the aircraft has to slow down to 100 miles per hour without altering height from 600 feet. At this speed the modern aircraft is just above stalling point, and Is inclined to wallow.

As the paratroops go out, the tail is lightened, which causes the aircraft to dive, unless carefully watched. The containers In the bomb -bay also fall away, further lightening the aircraft, and It requires great pilot skill to do a good drop where all the paratroops go out at the right height and speed.

PROBLEM IN DARKNESS This is hard enough in the day-

time, but to do it on a pitch-black night would seem almost impossible. And, because of the low altitude, it is no use trying to use the normal Radar devices, which show the terrain under- neath.

The use of Pathfinders, as in Bom- ber Command, with target Indicators, would be futile, for the glare of the indicator would attract troops from miles around, And, in any case, the degree of precision is not great enough for the purpose.

A special Pathfinder technique was thus developed for airborne work, The Pathfinder aircraft was fitted with "G" -radar, which tells the navigator just where he is (within a matter of 50 yards) at short distances from the

(Continued on Next Page.)

REBECCA 5E1

approximate area, where he requires his airborne force to go into action. Army and Air Force officers then go through aerial photographs and select likely landing or dropping areas. The enemy, of course, does exactly the same thing, and probably the most suitable landing places for gliders are obstructed with poles sunk into the ground and mines on top.

Surprise is a big weapon of an airborne force, and if anything goes wrong with this element, it becomes a helpless force. Such was the case at Arnhem. It is thus necessary to carry out the whole operation with clockwork efficiency and timed to the split second. And there is no room for near -misses on the part of Air

stant and the rendezvous will usually be between 10 and 15 miles from the field on which he has to drop the paratroops.

The trip from RV (Rendezvous) to the DZ (Dropping Zone) thus occupies between. five and eight minutes, and during this period the pilot undergoes a terrific strain. He has to lose

c

RECEIVER AERIAL

Showing how an aircraft equipped with "Rebecca' is guided by "Eureka" to the dropping zone. Despite its small size up to 300 aircraft may use

one Eureka simultaneously without confusion.

TRANSMIiIFI AERIAL

EUREKA SEI

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE THREE

FEATURE STORY

SNATCHED ALOFT BY A SPEEDING PLANE

Investigating all possible means of rescuing stranded airmen, the US Army has evolved a successful method of picking up human beings by a plane in full flight. The man who risked his life in the first hazardous experiment was paratrooper

Lieut. Alex Doster.

Since the first daring expe r i -

ment, other men have put the method to test and demonstrated the feasibility of rescue by, this.

means. Airmen's lives

were being lost by the failure of normal rés c u e means under certain conditions, and the Wright Field Equipment laboratory tackled the problem of direct human pickup. A chance of 1 in 25 of saving life was considered worthwhile, but it was reckoned too hazardous for immediate tests.

There followed weeks of exhaustive experiments with weights and sand- bags, and then a sheep was snatched aloft. But something went wrong with the

r

is

,

harness and the sheep was strangled. Subsequent tests with animals proved more successful and, ultimately, Lieut. Alex Doster volunteered to be the "guinea pig."

As a preliminary measure, Doster was trailed from the plane to test the harness-and this was fortunate, for a serious fault was revealed and recti- fied.

On the day of the test, Doster lay on his back with knees strapped up near the chin. A Nylon rope attached to his harness trailed up and over two slender poles, ready to engage the plane's trailing hook.

Travelling at more than 100 mph, the plane slid down between the poles and then shot up at a steep angle, carrying Doster with it. He was hauled into the plane, none the worse for the adventurous experiment.

"X" MARKS THE SPOT (Continued from Previous Page)

beacons which operate this equipment. But the "G" was only relied on to bring the aircraft within close ap- proximation of the DZ.

The navigator's eyes would take about 2ú minutes to become accustomed to the darkness after looking into the green glow of the cathode-ray tube, so it was left to the bomb -aimer to do all map -reading. The navigator and his "G" would tell the bomb -aimer what he should see and when.

The results achieved in this manner were amazing. On a pitch-black night, the Pathfinder aircraft could find by human eyesight one selected field in the middle of many other similar ones, and, after circling it, could drop down a "stick" of paratroopers.

The bomb -aimer is equipped with a special map of the area quite different from the usual map with black lines on white paper. Instead, it is grey, with darker parts indicating features of the land.

NIGHT VISION VITAL In the palm of his hand is a small

and very weak electric bulb, and he is completely obscured from other lights in the aircraft by a curtain. After half an hour the bomb-almer's eyes are fully adapted to night vision, and looking at the grey map with the shielded bulb does not blind him. With the aircraft flying only a few hundred feet up he can identify an individual field on the darkest night.

The paratroops carried by the Path- finder are specialists and so vital is their job that they carry all equipment with them when they jump. There is always the risk that, if the radio gear was dropped in containers, they might not find it in the dark.

Some carry equipment in special pockets running down the front of their legs; others jump out clutching a big kitbag, which they drop as soon as their 'chute opens. It falls down 15 feet on a rope and hits the ground before the paratrooper. This allows him to slow up and hit the ground at the normal speed, even though his 'chute has carried about twice the normal load.

The radio carried to the ground is known as "Eureka." It is very robust and consists of two boxes no bigger than the prewar portable. One is a special UHF transmitter -receiver; the other a power supply. A collapsible tripod is carried to hold the monopole aerial a few feet off the ground.

The paratroopers judge the wind and the Eureka is set up at a point outside the field, so that an aircraft flying dead overhead would lay its stick of paratroopers down the centre of the field.

The Pathfinder has probably been allowed half an hour or so to find the field and put down its Eureka team, while another Eureka team has been

(Continued on Page 12)

PAGE FOUR RADIO AND HOBBIES FOR DECEMBER. 1945.

MOW IT WORKS

i

Though you perhaps never thought of it, many calculations which concern you quite a lot-your income tax and bank liabilities, for example - are finally assessed on a mechanical calculating machine. Operated something like a type- writer, these machines answer arithmetical problems with an accuracy and speed

beyond human capabilities.

MITT their very speed and cóm plexity is itself a tribute lo

their inventors. To the uninitiated, the works appear just a hopeless jumble of wheels and pawls.

For centuries man has sought to in, vent machines which would undertake the tedious operations of addition, subtraction, multiplication and division.

Simple contrivances, such as the 'abacus, are of quite ancient origin, and even more complicated machines have been attempted over the last three centuries. However, the first calculating machines-which were designed in the 17th century-were of little practical use.

Modern calculating machines are compact and accurate. They range from the desk adding machine to the giant 35 -ton mechanical "brain" which has been in use by the US Navy for the past year or more.

Sketched here is the internal mechanism of a small calculating machine in the process of multiplying. The machine is capable of adding, sub- tracting, multiplying and dividing.

BASIC PRINCIPLE To multiply is merely to repeat a

set of figures a number of times, and then add them up. This explains the principle of the calculating machine.

Part of the sketch gives a diagram- matic representation of the arrangement of this machine. Seven teeth have been' set up on the multiplicand drum by an operating lever.

By forcing seven teeth above the surface of the multiplicand drum, this causes the figure -registering wheel to give the figure 7 for one complete turn of the drum.

Four turns will produce the figure 28, the multiplier wheel at the top of the machine registering 4.

Carry-over levers push deflector teeth over to operate the figure -registering wheel one unit at a time above a value of 9 on the unit wheel.

Division is obtained by turning the operating lever ìn an anti -clockwise direction and reading the answer on the top dial instead of the bottom.

Other kinds of calculations can be made with this machine.

In order to do away with the necessity of turning the operating handle many times in making a big calculation, it is necessary merely to move the carriage at the bottom to the right, say; to the third place, when the indicator shown in' the multiplier wheel dial will move. to the third place on the left. This makes it possible to

TWO OF EIGHT RED FIGURES FOR MULTIPLIER WHEELS AD ITION AND

SUBTRACTION

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CARRV-OVER LEVERS

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DEFLECTOR TOOTH

OPERATING` HANDLE t

WAGE

make a big calculation with but few turns of the operating hand.

For example, it is possible to multiply by 297 by setting the multiplier wheel to 300 ' and then going back three turns of the handle. This is much quicker than running the units 297 times.

At the base, just above the carriage, is a white number on a black ground. This is a check register on the movement of the carriage to the right.

PROBLEMS "IN TANDEM" The machine is re -set by returning

all figures to zero, including the levers operating the multiplicand teeth. If required, answers to successive sums can be "held" in the machine while other calculations are made, and then a grand total can be obtained with one turn of the handle. Many details of the mechanism have necessarily been omitted from this diagram of the machine's operation.

For the ultimate in complexity, it is necessary to consider the ultra -modern ready reckoner designed by Comman- der Howard H. Aiken', US Navy, pro-

fessor of applied mathematics in civil life,

This machine is 51 feet long, 8 feet high, contains 500 miles of wire connections,' 3500 multiple relays, 35,000 contacts, 2225 counters and tiers of 72 adding machines,

Problems that the machine can tackle include computation and tabu- lation of functions such as logarithms and . square roots: the solution of ordinary differential equations, and simultaneous linear algebraic equations, integral calculus, and statistical analysis.

Addition' and subtraction are carried out with the aid of 72 adding counters. each consisting of 24 electro- mechanical counter wheels, permitting computation to an accuracy of 23 figures. The 24th and highest -order counter wheel in each adding counter is reserved for the indication' of algebraic sign.

Multiplication is done with the aid of a mechanical multiplication table, which is also used in division.


RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE FIVE

POPULAR 'SCIENCE

Jr

n

A typical Australian cement works, at Kandos, NSW.

Your house probably has concrete in its foundations, and perhaps a lot more elsewhere in its structure. You walk on a concrete path to the station, and wait on a platform with concrete retaining. walls. You pass over bridges, canals, pipe- lines-all of concrete-and the walls of your office building are of the same versatile material. What is this all-pervading

medium, and who invented the stuff, anyway?

YOU buy it cheaply in handy powder form, mix it with the

commonest of ingredients, mould it into any shape and size you want, and there it stays!

Behind the development and manufacture of cement concrete lies an interesting story which very few people bother to think about as they tread the footpath on their way to work. Who would think that, behind those commonplace slabs, lies a history that goes back to the earliest times of man's existence?

Of course, I don't altogether blame people for not thinking about these things for, today, we have far more than history on our minds. More important to we suburbanites is the problem of paying the Council for the slabs of concrete on the front footpath. Then there is my own problem of convincing my wife that, because I am writing an edifying article on the manufacture of cement concrete, it does not follow that I can summon sufficient energy to start on the car drive I have been going to make for the past eight years.

Nevertheless, it is handy to know just how the stuff came to be developed. Next time one is mixing up a mess of concrete pottage and the small boy says, "Where did that stuff come from, Mister?" one can begin:-

Once upon a time, long before men bothered to write down the things that they did, it was thought that, instead of building their houses by standing one stone on top of another and trusting to luck that they stayed there, it would be a good idea if

something could be found to stick them together.

Of course, in those days, wolves were prevalent and they had a bad habit of huffing and puffing and blowing houses down and this made it most important that something should be done about it. So one day a good fairy came along and . . .

and so on .

Now this is a fact (all except the wolves and the fairy), for no one knows exactly when lime mortar was first used as a binding material. There is an an -

end of the eighteenth century . and it is this period which really dates the beginning of the modern cement industry.

It all began in 1756 during the building of the Eddystone Lighthouse. An English engineer, John' Smeaton, had been given the task of building a lighthouse on a group of dangerous rocks off the coast of Cornwall. The Eddystone rocks were under water at high tide and earlier wooden struc- tures did not withstand the elements for a long period.

SMEAtON'S EFFORTS Smeaton was determined to devise

a structure that would withstand the furies, btit his greatest trouble was with the foundations. Ordinary lime mortar would not harden properly.

Investigation by Smeaton revealed that the pure white limestone, thought best for lime making, was inferior to soft, clayey stone, and he actually obtained from this a lime that hardened better in air and also hardened under water. There was plenty of this stone near at hand and Smeaton used this as the basis of his cement in the construction of the Eddystone Lighthouse.

In 1796 a gentleman from Northfleet, in Kent, named James Parker, patented what he called a "Roman Cement," which he made by burning certain kidney shaped nodules called "sep- taria" and then grinding the product to powder. These nodules occured in the clay formation of London and were sometimes washed up on the shore.

By Calvin Walters

cient temple on Cyprus which is supposed to be the oldèst ruin in the world, and lime mortar was used in this to bind the stones together.

Four thousand years ago the Egyp- tians manufactured a concrete that has endured ever since and the cement used to bind together the stones of the Pyramids is actually harder than the granite itself.

The ancient Romans used a lime cement with which to build walls, aqueducts, monuments and roads and many of these still stand. Roman cement was made by grinding lime and volcanic ''ash together and this mixture was found to harden under water, being suitable for the construction of docks, baths, water cis- terns, &c.

It is rather strange that no ad- vance was made in the . matter from the the of the Romans until the latter

This Roman ^ement became popular as it was found' to be suitable for much work that could not be done with -

ordinary quick- lime.

The next stage was reached when Edgar Dobbs, of England, took out a patent in 1810 for the manufacture of a cement made by the admixture of carbonate of lime and clay, moistening the mixture, moulding into bricks and burning.

Then came the important event in 1824 when Joseph Aspdin, a brick- layer of Leeds, patented what he called "Portlan'd Cement." This he proposed to make by mixing limestone with clay and burning and grinding the mixture. The name "Portland," it is thought, suggested itself to Aspdin because of the resemblance that his cement had, when set, to the yellowish grey stone from the quarries in Port. land, England.

Portland cement is today manufactured in a different manner to the specifications of Aspdin. Aspdin did not burn his product to the point of vitrlfaction, as is done today, and the

PAGE SIX RADIO AND HOBBIES FOR DECEMBER, 1945

POPULAR SCIENCE

I I

results of his cement -making were a little uncertain. It was used mainly at first for stucco work but, in 1828, the cement from Aspdin's work was used in the construction of the Thames tunnel.

After 1843 improvements in the making of cement led to its more extensive use and, today, the product is manufactured to a definite standard. The name "Portland" still denotes a manufactured cement, no matter in what country it is made.

Cement can also be made from a natural rock found in certain parts of the world. In 1818 a natural cement rock was found in Madison County, New York. This was ground, calcined and used in large quantities for building construction. Later this natural rock was discovered in other parts of America and a place name Rosendale, in Ulster County, became the centre of the industry. The natural cements of America are called Rosendale cements for this reason.

Portland cement can be made from any materials that will yield by burning the chief components-silicates and aluminates of lime. These raw materials are usually classified under two headings: (1) Calcaeous, which include limestone, marl or pure carbonate of lime, and chalk; (2) Argil- laceous, which include clayey limestone, clay, shale and blast -furnace slag.

CHEMICAL TESTS The raw materials are subjected to

exhaustive analysis, as various chemical impurities in the materials may make it unsuitable for cement making. This "chemical control" is the starting point of cement manufacture of high and uniform quality. By this means the mixture of limestone and clay is controlled so that the final mixture contains bile correct propor- tions of silicate and aluminate of lime.

There are two processes for the manufacture of cement, the wet process and the dry process, and these have been the subject of debate for many years. Advantages are claimed for both.

The wet process is the older and is used mostly in Europe, whilst the dry process is mostly used in America. .

It is only in the treatment of the raw materials that the two processes differ, as the equipment used is much the same for each.

For the wet process the limestone and clay are crushed, mixed with water, then ground and burned whilst wet. The raw materials are fed into huge grinders, water added and the process continued until a 'soft, clayey mass is obtained, called a "slurry." This is kept stored until ready for feeding into the kilns for burning.

In the dry process the materials are mixed together and ground dry. In both processes the materials must be

i

A diagram plates end

illustrating the grinding sieves of the wellknown

ball mill.

ground to such a fineness that 95 per cent, of it will pass through a sieve having 32,400 holes per square inch.

The material is now ready for burning and, for this purpose, there are different types of kilns in use, the most popular being the rotary type.

The rotary kiln consists of a huge cylinder up to 12 feet in diameter and up to 250 feet long, made of steel and lined with fire brick. This cylinder is placed at a slight inclination from the horizontal and is revolved at from one turn a minute to one every two minutes by a special power plant. The material to be burned is fed into the upper end of the kiln and moves gradually by gravity to the lower end, where it falls out into receptacles.

The heat for the furnace is supplied by a jet of burning fuel, which is introduced into the lower end, and the hottest part of the kiln is main-

i

tamped at a temperature of about 2600 degrees Fahrenheit.

There are four zones in the kiln where different reactfonS take place. The kiln is not divided into actual compartments but the temperature varies along its length according to the distance from the fuel jet;

In the remote end the mixed ingredients are heated to a temperature which decomposes the carbonates, burns any sulphur present together with organic matter, and evaporates moisture.

UNDERGOES CHANGE In the second zone the carbonates

are finally decomposed and the third zone begins to heat the mixture to the temperature required for the formation of the necessary silicates and aluminates of lime; the fourth zone, which is also the fuel combustion chamber, fuses the mixture into the siH- cate and aluminate of lime, called cement clinker.

The fuel in most common use is pulverised coal but, in localities where it is economical to use them, fuel oil or natural gas is effective as fuel.

Correctly burned cement clinker is greenish -black in' appearance and of a glassy lustre; When just cooled it sparkles with bright glistening specks which are not present if the clinker is underburned; the lumps of clinker are about the size of a walnut.

The clinker emerges from the kiln at an approximate temperature of 2000 degrees Fahrenheit, and, before grinding, it must be cooled. This is done in a rotary cooler somewhat similar to the kiln with the difference that cool 'air is drawn through the cylinder. As the air ascends the cylinder it cools the clinker and at the same time becomes heated; it is thus handy as preheated air for forcing the fuel into the kiln.

Some manufacturers maintain that a better cement is made from a clinker that has been seasoned. The season-

(Continued on Next Page)

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Concrete en -masse. Looking, on the sloping well face of the Wyangala Dam, one of many in this country.

RADIO AND HOBBIES FOR DECEMBER, I94$ PAGE SEVEN

POPULAR SCIENCE

ARTIFICIAL ing is done by allowing the clinker to stand for a period of three months or more. . At the end of this period the clinker is artificially dried, for it absorbs moisture in various ways during the seasoning period.

Before grinding it is necessary to add what is called a retarder to the clinker, Cement made from clinker alone sets too quickly, making it difficult to work; the retarder, as the name suggests, retards the setting time of the finished product.

The retarder in most extensive use at present is gypsum; this has replaced the older plaster of paris retarder as it is equally as effective

ROCK. Continued and much less expensive. The, gypsum is carefully proportioned to the weight of clinker and, after the addition "o1 the retarder to the clinker, the mixture is ready to go to the grinding mills.

Grinding of the clinker is done in mills, of which there are several varieties. The ball mill is perhaps the oldest variety and is still in use today, particularly in Europe. It consists of a drum or cylinder containing over a ton of steel balls. The drum is made from chilled steel plates which over- lap one another, thus forming a series of steps around the inside circuinfer- ence of the drum. The clinker is fed

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11E4 As -the fallow increases the fertility of the soil, so

broadcasting enriches the mind.

But without clear enunciation and

reproduction, opinions of experts lack conviction.

Radiotron Valves are now available to bring radio entertainment back to its original standard.

REGULAR AND DEPENDABLE SUPPLY

ddot. of elmolgoo,oaed Woole.a roire Co. Pty. Lid.

into the drum and, as it revolves, the steel -balls drop over the steps and pul- verise the clinker.

The pulverised clinker drops through roles in the steel plates of the drum on to- perforated steel screens which are bolted around the outside of the drum; the very coarse particles of cement are held back by the screen and returned to the inside of the grinder .whilst the finer particles are allowed to fall on to a woven wire screen of the correct mesh. The fully ground material passes through this screen and the coarser particles are returned to the drum,

GROUND VERY FINE The latest type of grinding machinery

makes use of combinations of balls and rollers but all have the same aim, namely to grind the clinker into an almost impalpable powder. M mentioned above, the powder must pass through a screen having 32,400 holes to the square inch. The product . is now Portland Cement.

Now there is a matter that puzzles a lot of- people regarding cement. Why does cement set into a hard mass with

-the addition of sand and water? It seems contrary to all expectation that, when you add water to anything, it should set into a stone -like mass.

The theory of the setting of cement is not easy to explain in a popular treatise of this nature, as it necessarily involves certain chemical reactions, and these cannot be explained in very simple terms.

Several theories have been advanced as to the setting of cement, but the modern idea is that given originally by a chemist named Michaelis in 1893, and confirmed during the last twenty years.

This chemist suggested that the hardening was due to the formation of colloidal calcium hydrosilicate. Cal- cium is, of course, the lime. and its action on silica (sand is a form of silica) forms calcium silicate; the addition of water forms calcium hydro - silicate. A colloid is a term used here to denote something that is in the nature of a glue.

WHY CEMENT SETS Familiar colloids of this nature are

gelatine, starch, jgum, albumin, Sac. Thus in Portland Cement, when water is added. it takes the lime content into solution; this lime solution in turn acts on the silica and alumina in the cement and forms a jelly -like mass with properties very much like glue. The water is absorbed by chemical action or dries out and the colloidal mass becomes hard and dense.

The process is called the hydration -

of the cement and the change from the plastic state to the solid is termed "setting." After setting, a gradual increase in strength takes place and this is known as "hardening." The full strength of cement is not attained until a period of six months to a year has elapsed. -

There have been several experiments


PAGE EIGHT RADIO AND HOBBIES FOR DECEMBER, 1945

AVIATION

It was disclosed ea r l y this year (1945) that the Japanese had two new 400 - miles -an -hour fighters in service, and many other planes which showed marked technical improvement over earlier models. But even these new Japanese - planes were hardly a match for machines like the Mus- tang, Lightning, Thunder- bolt, Spitfire, Hellcat and Seaf ire.

THE US magazine "Flying" com- mented early this year that,

generally speaking, the same difference between the Japanese and the American planes existed then as in the early part of the war.

Japanese fighters, it was pointed out, could still out -manoeuvre ours, but they could take much less punishment.

Sketched here are three of Japan's last military types, two of them machines turned out from the Naka- jima factories and one from Mitsu- bishi.

These machines were seen in use on nearly all fronts in the months preceding the Japanese surrender. Like other Japanese planes, they were given nicknames by Allied airmen to facilitate identification, and these, adopted, as code names, have become "official" designations.

CAPTURED "SAMPLES" Sketches here are based on machines

which fell into Allied hands. The "Jack" (upper left), built by Mitsu- bishi, is a. Navy fighter powered by a Mitsubishi Kasae twin -row radial engine of 1870 horse-power, driving a four -blade propeller.

The Mitsubishi Kasae twin -row was a new fan -cooled engine. The fan made a terrifying noise, particularly when the plane went into a dive.

The Jack, with an 1100 -mile range. has an unusually large fuselage for a Japanese fighter. Armament consists of two 7.7 mm. machine-guns and two 20 mm, cannon, or four 20 mm. cannon, the same size as those on the notorious Zero, but with considerably higher muzzle velocity,

Wingspan of the Jack is 35ft. Hin and length just over 30ft.

The "Frank" (top right) is a single - seat, low -wing monoplane, built for the Japanese Army by Nakajima. De- spite high top speed, it has quite good low -speed manoeuvrability, though some of the nimbleness of earlier and slower machines is lost.

The lightweight Zero had gone into action without armorplating or fuel

i

i- NAC3IMA ,FgANK' -

in the form of coded tape, the machine responding to the tape markings through numerous internal operations.

The code gives the machine three jobs. It directs the machine to take a given number or series of numbers from a particular storage device; it directs where the number or series is to be placed; and then it directs what is to be done with the numbers. The answer appears either on a sheet of

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tank protection, and, largely on account of the surprise factor, it won many combats in the early days of the Pacific war. But, when the novelty value had gone, the Zero suffered heavily at the hands of Allied pilots who had learned its tricks.

The Frank is an improvement on the Tojo fighter, itself an adaption of the Oscar. The Frank was actually the top-ranking army fighter at the time of the surrender.

Power from its 2000 -horsepower Nakajima radial engine is absorbed by a four -blade propeller, giving a speed of about 420 miles an hour at 20,000 feet. Range is approximately 1700 miles.

As usual with Japanese fighters, landing presented problems, and highly -skilled pilots were needed to handle the machines. Wingspan of the Jack is 37ft. 4tn., and length 32ft. 4M.

Nakajima's torpedo -bomber, the Jill (below), was a low -wing mono -

plane in extensive use by the Japanese Navy. It is powered by a single Naka- jima radial motor .driving a three - blade propeller. -A feature of the design is the tall,

angular tail -fin and rudder, beneath which is a remotely -controlled machine-gun.

Another characteristic feature of the Jill is the long "glasshouse," which includes the pilot's cabin.

Many of Japan's aircraft were quite good, and well suited to their tasks. But the number of skilled Japanese pilots diminished rapidly, and the shortage of competent aircrews was a fatal weakness in the organisation, after the first flush of success was followed by a struggle on equal terms and then at increasing odds.

In addition, Japanese air power lacked flexibility, and the aircraft types failed . to provide the! almost endless variety which has been such an outstanding feature of Allied aircraft- and such a vital factor in victory.

MACHINES KNOW THE ANSWERS I (Continued from Page 5)

Problems are fed into the machine teleprinter paper or on a punched card.

The code book, which is essential to the operation of the machine, covers every known type of mathematical problem.

The operator of the machine does not have to be a trained mathematician, but a mathematician must prepare the problem by using the code book, so that the operator may punch the code holes in the tape which feeds the problem to the machine.

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE NINE

MODEL' PLANES

BUILD THIS SIMPLE FLYING MODEL THE simple design was chosen

deliberately, for it was realised that it might be the first flying model for many of our younger readers. Furthermore, the materials required are such as can be obtained from some of the model flying kits now on sale in many toyshops.

The supplies of balsa, rubber and small parts will soon become more widely distributed than now, and we will feel at liberty to pursue a more ambitious programme in this intri- guing and fascinating hobby.

The model we are about to describe is really an adaptation of the ever - popular all -balsa hand -launched glider, and, as such, is capable of really interesting performance..

We have endeavored to keep some similarity in appearance to that of a fullslze aeroplane of the high -wing type. Thus, although it is really a stick model, we have used a deep side silhouette plan to secure a measure of likeness in that regard.

The complete structure, with the exception of metal parts and the rubber motor, is all balsa, and, in- cidentally, the motor may well prove to be the hardest part to secure. It Is just about as simple to con-

struct as a flying model could be, and, due to its rugged lightweight construction; it is capable 'of flying quite well and standing up to the hard knocks it will probably be called upon to take.

The Job flies quite fast, has an excellent steep climb and a fast flat glide. Given extra power in the form of more rubber strands on the motor, it will turn on some crazy aerobatics.

NECESSARY PARTS Before starting on the construction,

it will be necessary to get together the required materials, and we suggest that you tackle this problem in somewhat the same manner as we did. By check- ing up on various commercial solid model kits, you should be able to secure sufficient flat balsa stock to duplicate

It is quite a long time since we described o flying model in these pages, due to scarcity of materials and the general pre-occupotion of enthusiasts with solid models f o r recognition purposes. However, it should not be long before flying models take the air in force again, and we set the ball rolling this month with an elementary but nevertheless efficient little plane.

sold by stationers can be knotted together to stretch from nose to tail. They make a reasonable substitute for the more usual flat or square section aeroplane rubber.

Now to the actual construction, which is really very simple. Take a piece of fiat balsa wood and sand down smoothly until it is 1-161n. thick. Using the diagram of the wing in our plan, transfer the sizes to the balsa and be sure you make a right and left-hand side. Having done this, you cut out both halves, using a sharp knife or razor blade.

The edges and tips of these wing - halves are now nicely smoothed with tine sandpaper. The top of the wing may be sanded to the slight aerofoil section noted in the drawing. Might we mention here that this Is not an absolute necessity, but is rather in the nature of a refinement, which will have a beneficial bearing on the ultimate performance of the model.

When nicely smóothed up, the two halves' are cemented together, and, to secure really good stability in flight, it is necessary to add what 1e known as dihedral angle. This is nerured by een-

at the nose per medium of the propeller bearing, which is preferably made of sheet aluminium. The hole in this bearing may be drilled with a fine drill or punched with a gramophone needle. It is advisable to bind the bearing in place with fine thread, cementing over the top for good measure.

Using the plan as a guide, next cut out the fin and the tailplane to shape from nicely -sanded balsa about 1-321n. thick. Cement the two surfaces together and attach them in the same way to the rear of the fuselage. Make sure these square up nicely on the fuselage, as the tailplane has a big bearing on flight performance.

The tall hook Is now bent to shape, and attached to the rear of the fuselage. It is very necessary to see that it is securely attached, because ft has to stand the pull and twist of the tightly wound rubber motor.

PLACING THE WING The wing can now be attached to the

fuselage and securely cemented in position. It is very important to see that the wing is so placed that it forms the same angle on each side with the tailplane when viewed from the front. Otherwise the ship will be hard to adjust and fly.

The propeller is undoubtedly the hardest part to duplicate, and it is the most important single item in the success or otherwise of the model. Start the job by squaring up a block of balsa to the dimensions noted on the plans and then cutting out the block to the blank shape. Taper this blank, as shown in the side view of the propeller blank, and then commence carving operations. The diagram will most probably be your best guide in this matter.

To secure the required pitch angle, the blades are

By Jack carved from corner to corner and

4 taper from about 1 44_104.. ..<,.,. ,_

the wings and tail sections from the parts included in these kits for the same purpose.

The propeller block may well be secured in the same manner, but, in all probability, it will be necessary to shape a fuselage block to the required dimensions for the propeller. The wheels, metal parts, glue, &c., can be nbtained from this source. Should you have any difficulty in this matter, it would be possible to get the wire scraps from anyone doing piano repairs, and a hunt round the house should bring to light some flat metal suitable for the propeller bearing.

As we mentioned before, it may not be possible to secure suitable rubber strands for the motor, but there is an alternative. Rubber bands of the type

ing one wing half flat on the working board and raising the tip of the other half three i nches high, cementing them in this position.

Make doubly sure you have a good joint here. It is a wise precaution to build up a fillet of cement along the joint, because it is here that the wing takes the most strain.

The fuselage of the model has been reduced to a very simple operation, and the plans give the key to the construction. Very little shaping is required. The wing position is cut in so as to leave the front edge of the wing 1-16in, higher than the trailing edge.

The two sections are joined together

Finneran the centre to 1-16 in, at the tips. After carving, round the blade

shape and sandpaper to a nice smooth finish. Pierce the centre hole and check for balance. The propeller shaft is now bent to shape and attached.

To obtain smooth running, it is advisable to slip a small glass bead on the shaft between the propeller hub and the front bearing.

The plane is now complete, but, to enhance its appearance and add to its strength, it is advisable to give it a few coats of clear lacquer and to sand all surfaces to a nice smooth finish. This finishes the job ready for flying.

Loop a couple of strands of 3-161n.

PAGE TEN RADIO AND HOBBIES FOR DECEMBER, 1945

MODEL PLANES

WING PLAN I.16"%THICK BALSA SPAN 14"

RUDDER PLAN ' -SIDE VIEW

PROPELLER

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flat rubber or its approximate equiva- lent in rubber bands between the hooks and the job is ready for its first flight. Make sure that it balances at approximately the position noted on the plans as this will ensure a minimum of adjustment to secure the desired performance.

Wind the propeller until a full row of knots shbw on the motor and then spear the model gently away from you, letting the propeller go at the moment of release. If the job has been carefully made, it should climb swiftly away from you and commence turning to the left.

If the model shows a tendency to nose-dive, it can be corrected by warping the rear portion of the tailplane up or adding a small amount of weight to the rear of the ship.

Alternately, if it shows a tendency to nose up sharply and then flop down again, flying in an undulating fashion, it will be necessary to add weight to the nose, until a smooth even climb and following glide is attained. Inciden- tally, plasticine modelling clay makes an excellent adjustable weight.

The plane can be made to turn in any direction by suitably warping the rudder and wings, and experimenta- tion will give you the necessary information in this matter.

To make the model rise from the ground it will be necessary to wind the motor fully and place it on a smooth piece of ground. On releasing the model, it should scoot along the ground and rise swiftly into the air.

By adding extra power and experimenting you should be able to secure a variety of stunts, but we suggest you

become very familiar with the vagaries of your model before attempting aerobatics.

We hope you will have a lot of fun building and flying this little midget. Perhaps, in the not -so -distant future, model aeroplane building and flying

\will attain an even greater measure of popularity than it enjoyed in the prewar years.

TWO NEW DRUGS DEVELOPED DISCOVERY by British chemists of

a revolutionary new drug for treating malaria was announced recently by Lord Leverhuime.

The new drug, called paludrine, is the most powerful anti -malarial weapon yet produced.

One part of it is equal to three parts of atebrin, or 10 parts of quinine.

It is easier to make than atebrin, and does not produce the yellowing effect on the patient, which is the most undesirable result of atebrin treatment.

Extensive clinical trials in Australia established that paludrine is not only more effective, but less toxic, than either atebrin or quinine.

Its prophylatic action has not yet been completely tested, but it is be-

lieved suitable dosage may afford complete protection.

Its value in preventing relapses is not yet fully established.

A NEW child -birth anaesthetic can be self-administered from a pen-

cil -sized container, to which an india - rubber mask is attached.

It is a drug called trilene, which smells like chloroform, but leaves no unpleasant after-effects.

"Trilene has been successfully used in a number of maternity hospitals," according to Dr. J. Flam, of London.

"When a woman feels labor pains coming on, she can pick up the face - piece and inhale the anaesthetic.

"She cannot give herself an over- dose."

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE ELEVEN

FEATURE STORY

"PALEC'RADIO and ELECTRICAL TEST EQUIPMENT and METERS

Volt Ammeter P.M.G. No. 4 Detector

Model MPT Industrial Maintenance

Tester A.C.-D.C.

Model VCT Valve and Circuit Tester

"Major" Laboratory Type 30 Range Multimeter

"Vibro-meg" 500 Volt Self-contained

Insulation Tester

Model MCA Radio Service Multi -teeter

'X' MARKS THE SPOT

(Continued from Page 4)

put down at the Rendezvous. The main stream would by then be Only 60 miles from the Eureka at the RV, and would have their Rebecca sets on and getting a return from the Eureka.

The Rebecca set carried in the aircraft is very much akin to the ground radar set for locating enemy aircraft. It consists of a small low -powered UHF transmitter, which sends out short impulses.

The impulses last for less than a millionth of a second and occur only a few times per second. Because of this intermittent operation, the transmitter handles a signal out of all pro- portion to the strength It could carry if the signal had to be continuous.

The impulse, if within range of the Eureka aerial on the ground, causes this receiver to build up a current which triggers off a transmitter on another frequency, but using the saine aerial. The return is almost instantaneous. This second impulse travels back to the Rebecca set In the plane. where it Is interpreted into distance.

CATHODE-RAY TUBE A cathode-ray tube is set up in the

plane with a graduated screen, reading 0-15 and 0-75 miles along the sweep. With every impulse sent out from the plane the trace begins to move vertically at a predetermined speed. By the time the, original impulse Is returned on the different frequency from the Eureka on the ground, the trace has travelled a certain distance, de- pending on the time it takes the radio signal to cover the distance and return.

The returning signal is fed to the horizontal plates and the trace "blips" out, as indicated. The blip coincides with the reading '.on the graduated screen and indicates the distance in miles. Two ranges are available by altering the trace speed; the slow trace gives long-range readings. 0-75 miles, and the fast trace gives 0-15 miles very accurately.

The knowledge of distance is in- valuable in timing and losing height before a drop, but it is not, ninrh ncn

j Mnufscfurte f Y Types of Rd.o 8 EIctrricI Ted Equ;pmn1 1 1"41n.

90 VICTORIA STREET, ASHFIELD, SYDNEY.

Tels.: UA 1923:19604982. Telegrams: "Palcc."

PAGE TWELVE

l.alil// G PTY. (.TO.

without direction, and this is simply obtained by 'fitting an aerial: on each side of the aircraft' for --receiving the returned 'impulses,

The aerials are used alternately more than 30 times a second, and the signals from each are simultaneously fed to respective horizontal plates in the cathode-ray tube. This causes a double blip along the trace line.

When the aircraft is pointing directly towards the Eureka, both are or equal length. Should the aircraft point away from the Eureka one aerial will be shielded somewhat and the signal intensity will decrease, making a small blip on one side. This indicates to the navigator which way he

(Continued on )

RADIO AND HOBBIES FOR DECEMBER, 1945

FEATURE STORY AERO JET ENGINE BRITAIN has a new jet

engine even more powerful than the Der- wents fitted to the Gloster Meteors, which are being

to attack the world speed record, says the aeronautical corre- spondent of the "Daily Mail."

The new engine is the Rolls-Royce Nene. Cabinet Ministers and rep- resentatives of the Dominions and ./A rd and neutral countries inspected it at Farnborough aircraft exhibition.

The Nene develops a thrust of 50001b, which is 10001b more than that of the Perwent. A similiarly designed engine in America's "Shooting Star" gave the plane a performance superior to that obtained in the American - built turbo jet, with which it is normally propelled.

The Nene was designed and built in five and a half months.

* * *

METEOR'S 604 MPH FLYING the jet-propelled Gloster

Meteor, Group -Captain H. J. Wil- son established a new world's speed. record of 604 mph. The flight was made over the official course at Herne Bay, Kent. Only two-thirds of the jet's power was used and still higher speeds are expected after further experiment.

SCIENCE ON THE MARCH WALKIE-TALKIE TAXIS FORMATION of a fleet of radio -

equipped taxis is proposed by the Guild of Taxi Cab Owners.

The guild was formed early this year, and the,secretary, Mr. L. Earle, said it would attempt to end the racketeering which had brought the industry into disrepute during the war.

Radio -equipped cabs would enable prompt and efficient service to be given, Mr. Earle added.

* * *

WAR PLANES ON SHOW TtIREE British war planes-until re-

cently on the secret list-appeared at the recent Farnborough aircraft exhibition in England.

They were the Vickers Windsor, a four-engined bomber capable of carrying 12,O0Olb. bombs 1800 miles; the Bristol Brigand, a twin-engined torpedo bomber; and the Martin Baker, a single -seat fighter with a Griffon engine.

THIRD -DIMENSION FILM THE first full-length three-dimen-

sional film ever , made, entitled "Robinson Crusoe," is nearing com- pletion on Russia's Black Sea coast,

The film is in color and objects standout from a specially constructed screen as though they were real,

The Soviet film chief, M. Alexei Andreievsky, is producing the film.

* * *

AUTOMATIC BOW FRENCH troops have captured an

Annamese weapon, known as the "Tommy -bow" (named after the Tommy -gun) at Saigon (Indo-China).

The weapon is a type of automatic bow, which shoots arrows at the rate of five per clip from its magazine.

Discovery of the "Tommy -bow" was made after the capture of a bow and arrow factory.

* * *

MINE DETECTOR IN PEACE SPECIALLY adapted Army mine de-

tectors will locate the nails is salvaged timber before it goes to the sawmills.

The British Ministry of Works has ordered a detector, so that its peacetime uses could be examined.

Ministry officials say lost keys and coins can be recovered, and wires and pipes can be traced in walls and floors.

* . * *

SILK FROM TAR MOSCOW shops are displaying stock-

ings made from tar. They cannot be distinguished from real silk.

The stockings, made from a sub- stance called "patron," last three times as long as silk stockings.

"Patron" can also be woven into dress fabrics or made into solid lorry tyres.

'-mrsJX,

Large and small in helicopters. The picture above shows PV3. built for the US Navy and Coast- guard by the P -V Engineering Forum, Inc. It is claimed as the world's largest. On the right, the "Helicospeeder," invented by Antoine Gazda uses jet propul sion and lacks the usual tail rotor for steering. A top speed of 300 mph is expected by the inven- tor, who sees in the design the

possible "family buggy."

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE THIRTEEN

FEATURE STORY

KINGSLEY DOES IT AGAIN !

"FERROTUNE" Another

Major Technical Development

By KINGSLEY

Announcing the first of a series of Gangless Tuning Units- "Ferrotune" is a device which tunes a Radio Receiver

WITHOUT the use of a conventional -gang condenser.

FREQUENCY COVERAGE 540 KC to 1650 KC

eech revolution of driving knob equals 100 KC.

is DIAL READING Straight line tuning all over dial.

is MECHANICALLY SOUND Robust construction, wall engineered for long service under all conditions.

TRACKING Unit lined and track- ed during manufacture. No padding or matching, simply trim pointer to local high. est frequency' station.

KINGSLEY RADIO PTY., LTD.

225 Trafalgar Street, Petersham, N.S.W. LM4468. 380 St. Kilda Rood, Melbourne, Vic. MX1159.

From Australia's leading distributors.

'X' MARKS THE SPOT

(Continued from Page 12)

should turn to point to the Eureka again.

Of course, an aircraft seldom points to the place where it is heading, and the navigator has to learn to judge just how much bigger one blip should be than another, to allow for drift and to keep the plane on a straight track to the Eureka.

Each Rebecca set is fitted with a push-button selector, which gives six different transmission channels and Six different reception channels. This gives 36 different combinations and makes it most difficult to intercept unless the channels are known. The Eureka operator can also send messages from the ground to the oncoming planes in Morse by using a Morse key to col- lapse the blips, by cutting the Eureka transmission,

One of the strangest features of this device is that almost any number of planes can home on one Eureka. It supplies returns for more than three hundred Re- beccas at one time, but does not confuse the signals. This Is due to the extreme shortness of each ircoming pulse. In the main stream of paratroop

droppers bearing down on the RV, the navigators would be watching the CR screen and homing their aircraft over the RV at the correct moment. Let us suppose a fog has moved in over the dropping zone.

PIN -POINTS FIELD As soon as the plane is within a

mile or so of the rendezvous, the navigator gives the pilot a course to turn on to that should run them over the DZ. With the push buttons he changes from the RV Eureka to the DZ Eureka; he then steers the plane over the DX. Then, as the plane reaches a point exactly over the Eureka, the blips on the CR tube col- lapse. At this point the paratroops start to drop and will land in fog on the unseen field.

These paratroops would probably be used to remove the posts and protect the field for the gliders to come in later. And the glider tugs could use the Eurekas to home over the flare- path laid out by the paratroops.

This is how the airborne invasion of Europe was successfully carried out. Radar was the Allies' V -weapon, number 1!

! KR1255

MA 'E FOURTEEN RADIO AND HOBBIES FOR DECEMBER, 1945

quirea. 10. Installation

in a car involves some awkward physical toil and perhaps a few hours' experimenting with a handful of suppressor resistors and condensers.

Consider first the physical requirements of a car set. All cars differ in panel and bulkhead layout, so that an installation which suits one type of car will not always suit another.

Commercial set manufacturers meet this situation by making their products as versatile as possible, to meet carefully studied requirements. Most of them have a standard line of at- tachments dial -faces, &c., specially intended to match the layout and appearance of the well-known makes of Cars.

f I. Lie 4L2 LAeL, Al1U the power output

and supply system are all separated and tucked away in the most convenient corners.

A third and obvious alternative is to have the whole receiver as a single composite unit, but reduced to the smallest possible dimensions for ease of installation.

Whatever method is used, careful thought must be given to the matter of the controls. They must be situated in such a position that the driver can manipulate them without diverting his attention too much from the road. Or they may be placed where' only the passenger can operate them while the car is in motion.

Some cars have a lot of room behind one sida or the other of the instru-

vn. ul A l II IJVRIIQYIVL. Speaking generally, the system should

be favored which requires the least permanent mutilation of the car itself. Vacant panel -holes and cut-outs from some previous radio installation do not exactly enhance the appearance or the va;ue of a vehicle.

Seeking to approach the problem from the same level as the average homebuilder, we finally built up a receiver using standard parts, and the facilities available to most readers. The rest of the. article deals largely with this experimental receiver. Firstly, from the physical viewpoint,

it was decided to construct the receiver as a single unit within a metal case. A chassis measuring gin. x 7iin.


RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE FIFTEEN

CONSTRUCTION

NOW TO: BUILD AN AUTO RECEIVER With thoughts turning once again to the open road, many readers are apparently toying with the idea of building a radio for the family car. But very few realise just how tricky a job it really is, or how much work is entailed before the receiver becomes a source of pleasure. However, the following article describes o practical receiver and gives various pointers on its construction.

QUll introduction to the subject is framed in rather restrained

ternis, and this is quite deliberate. One runnot expect to build and instal a successful auto receiver without at least a fair background of set construction or radio servic- ing. If you want to build an auto set, we'll show you how to do it; but not without emphasising the problems which have to be faced.

It would not be extravagant to say that a car radio is perhaps the most difficult of all to build and instal. And, if you are dubious, here are some of the reasons: -

1. It must be physically compact and designed to fit into a selected spot in a particular make of car.

2. Since it must operate with a restricted aerial and in the open country, It must be very sensitive, but not noisy in operation.

3. The considerations of compactness and'hlgh gain must be achieved without tendency to instability,

4. An effective AVC system is essential.

5. Good power output 1s required, but economy of battery drain has to be considered at the same time.

8. It must be robust enough to withstand constant bumping and vibration.

7. The whole receiver must be completely shielded.

8. Elaborate precautions sary against vibrator hash and engine noise.

9. A remotely controlled d i a 1

and volume control are often re-

are neces-

Figure I, A view of the completed experimental receiver. intended to mount on the engine bulkhead just behind the

gear lever. Bowden cables operate the tuning and volume controls. The metal cabinet and speaker grille are essential for shielding purposes.

Unless very fortunately placed, a home builder has no access to this specialised material, and some hard thinking is necessary to adapt standard components to the requirements of a particular installation, Fortun- ately, there is no need to worry about things from the production point of view, so that quite tedious adaptations are permissible.

Auto sets are commonly built In two or more units. Sometimes the receiver is built as a complete unit and the loud -speaker arranged so that It can be mounted on the header bar, above the windscreen. Such a position has acoustic advantages, but calls for nice

workmanship if the interior ap-

W. N. Williams

pearance of the car is not to be compromised.

Sometimes the loud - speaker,

ment -panel, allowing the receiver to mount completely out of sight. The controls protrude right through the panel, or else are located on a false panel in the glove -box recess.

Alternatively, the set may be constructed with a small horizontal dial an the whole assembly so arranged that the dial and control protrude only beneath the lower edge of the instrument -panel. The bulk of the receiver is out of sight up behind the panel,

BULKHEAD MOUNTING Still another passibility is to mount

the receiver against the engine bulkhead, with a couple of Bowden cables leading up to control -knobs on the instrument -panel or the steering - column.

Each system has Its own advantages and drawbacks, and' must be considered on its merits for any par-

CONSTRUCTION

AUTO RECEIVER -Continued x 3in. was "unearthed" and adapted far the purpose by dint of much hard sawing and filing.

A sheet metal company was then induced to make up a complete rect- angular box of ordinary radio chassis steel, which actually measured loin. x Bin, x 8iin. high. This was to be fitted against the bulkhead and behind the gear lever of an ordinary sedan car, where it is out of the way of either the driver's or the passenger's feet. The speaker faces outwards towards the front seat, as is usual in many Commercial installations.

R.F.C.

the frequency to which the receiver is tuned.

Two such controls are required -one for the tuning condenser and a second for the volume control potentiometer. This latter can well be of the type fitted with a switch, so that the same cable will serve to switch the receiver off and on.

The complete circuit diagram is shown at figure 2. No attempt has been made to present a wiring diagram or parts list. In all seriousness we reckon that, if you cannot work these things out for yourselves, it were

6117-1

The original receiver used the new Kingsley iron -clad coils and IF transformers and proved to be extremely sensitive and selective. In fact, the IF amplifier valve could actually have been over -biased, much more Without reducing the sensitivity below that necessary to tune all worthwhile signals.

A special aerial coil is desirable in an auto receiver, but we found the standard Kingsley Permaclad unit to be quite effective. Sensitivity at the H.F. and of the band may possibly be improved by a small amount of direct capacitive coupling from aerial to grid; an open "postage stamp" trimmer between the two pins on the aerial coil, for example.

686-$ 6V6-G(r)

Metal Case RC. ¶.1 r-----

ósuH Ì

b I R.EC(

<2.* R.F. f.

f I s 25 .0011.-- - - ---

*0,3 d -e resistance a sirigT Pointpe Choke `earth_ Shiolded

Figure 2. The circuit diagram of the auto set. Complete filtering and shielding, as indicated, are essential for good results. The vibrator supply is contained within a metal box, earthed at one point only, and the input and filter system must be isolated from "hot" tuning circuits. The three chokes marked with an asterisk must be filament -type chokes of low de resistance.

5w.

01 11 To All

Heaters

It is suggested that this method of construction is the one likely to meet most requirements, although it can be varied if desired.

No standard chassis is available for this set, so that it will be necessary to follow our lead and make one-or have one made-to suit the components on hand. The parts position is still too uncertain to warrant a special design.

An immediate problem is that some remote control system is necessary for 'the tuning dial. We managed to obtain an old dial mechanism for the job, but one could be made from speedometer .cable and parts. The basic requirements are illus-

trated in figure 3. The cable connects through to a spindle on the chassis, which drives the condenser through a eduction gear of any suitable type. Another reduction gear at the control end drives a pointer to indicate

best that you did not tackle the job. Once again, it is not a job for beginners.

The main part of the circuit is seen, to be a straightforward 5-valve superhet, with an RF stage ahead of the converter. There are âne or two points Worth noting.

Firstly, we counted on a high-tension voltage of 'about '200, so that one or two dropping resistors are smaller than usual. . The lower voltage makes for economy and still allows the output valve to delivers, couple of watts. This is enough in a reasonably quiet car and is certainly enough for the 5 -inch loud -speaker in the metal cabinet.

No provision has been made for tone control or negative feedback, treble accentuation being an advantage, if anything. The first three valves are ests of stability, and rather more thorough AVC filtering than usual is employed for the same reason.

C:a6me}S

In assembling the receiver, remember that it will have to take a lot of punishment in the way of vibration, &c. Mount each component firmly, fit a lock washer under every nut and tighten well. If any major component tends to vibrate on its mountings, strap it dawn so that it will not work loose later on.

KEEP. WIRING RIGID The same care is necessary with the

wiring. Don't have heavy condensers, &c. floating around on the end of long pigtails. If they are not held down rigidly, bind them in place with thread, or wrap a piece of tinned busbar around them and solder to an earth lug.

You may or may not choose to follow our original design in detail, but various precautions must be observed in any case.

From the point of view of performance and stability, the signals must follow an orderly progression around

PAGE SIXTEEN RADIO AND HO881ES FOR DECEMBER. 1945

CONSTRUCTION

'',,SW:405i :eeJ!fi.i.ivo r..r4i,,ei,t4lee rJ

Figure 3. A remote tuning control may be improvised along the lines illustrated above, using two discarded but freely running dial mechanisms. Note that the cable must rotate et a much higher speed than the dial spindle,

and that the latter is insulated.

the chassis and no long "hot" grid and plate leads can be afforded. Shield the entire volume control and audio input grid circuit, and.keep the output plate lead away from other wiring.

Make the coil mounting bracket out of aluminium if possible, and return all AVC bypass condensers to it. The mounting position of other screen and cathode bypass condensers is less critical, but they should be mounted as close as possible to the point which they are intended to bypass.

A vibrator -type power supply is the obvious answer to the high-tension supply problem. Batteries are unsuitable for the purpose, and rotary con- verters are not so attractive for the comparatively low wattage r equrr ed.

To avoid the need for a separate rectifier valve, as in the emplrfier described last month, it was decided to employ a synchronous vibrator in a self -recti- fying circuit, It is rather more critical of adjustment, and those with strong feelings in the matter may incorporate a valve rectifier, if they so desire.

Figure 4. A view of the chassis, with the cover removed from the vibrator shield case. The output valve in the foreground is actually an 89, used because ii happened to be on hand. The 6V6 -GT specified is

more efficient.

In a compact design, some trouh'- can be expected from vibrar hash. but two basic precautions will save a whole lot of worry. In fact, we will go so far as to say that you MUST do these two things. Firstly, mount the tuning condenser

on bakelite or rubber bushes, so that the frame is completely insulated from. the chassis. Yes, rubber or bakelite above and below, the chassis bolts and a sleeve around them where they pass through the metal.

Check the insulation with an ohmmeter and then take three insulated wires from the wipers to the aluminium coil bracket or to a single point on, the steel chassis. This point also becomes the "rendezvous" for the AVC bypass condensers and as many of the others as can be managed con- veniently.

Purpose of all this is to keep the circulating eddy currents from the vibrator transformer out of the tuned circuits.

For the system to be fully effective, the mechanism of the tuning dial enlist also be insulated from the gang -shaft. A fibre instead of the usual brass bush is generally the easiest way out of this difficulty, The second "must" is that the

vibrator power suppiy system must be contained in a complete metal box. The exact parts thus enclosed are indicated on the main circuit diagram.

This vibrator böx may be made of chassis steel or, as in our case, of two thicknesses of ordinary galvanised flat iron, cut to shape and soldered at the corners.

The vibrator socket and transformer were mounted on a piece of flat bakelite, with a long bolt protruding downwards at each corner. All necessary wiring was then carried out, and, taking care that no shorts could


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RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE SEVENTEEN

CONSTRUCTION '

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occur, the unit was slipped down into the metal case, the long bolts protruding through holes in the bottom.

A piece of masonite, shaped to correspond with the bottom of the vibrator -box, was then added, and this formed a layer of insulation between the box and the chassis.

But . the mounting -bolts must not touch the metal where they pass through the chassis, All are insulated except the one farthest from the tuning circuits, and this bolt forms the one and only earth connection between the vibrator - case and the main chassis. The leads for 6V. input and HT

output should pass down through the box and chassis at a point where they are most convenient to the filter system, yet to be described.

A point to watch is that the gang condenser and the vibrator -case re- main well clear of the metal cabinet in which the receiver has finally to be installed. If; one or both were to touch this, all the careful one -point earthing would be rendered useless.

CHECK POLARITY Before the vibrator supply is finally

installed, it is as well to check the connections to the vibrator. With a synchronous vibrator system, the phase relationship of the windings determines whether the HT output shall be positive or negative in sign.

So before the electrolytic condenser is wired in, and before the final installation is made, operate the vibrator for an instant and note whether the output is positive or negative.

Changing over either the primary or the secondary transformer connections will alter the sign of the output.

Make sure that you get the primary voltage the, right way round while carrying out this test. In most ears the positive batteri' terminal Is earthed, so that Your active lead must go to -6.0v. Most auto service manuals list the polarity of auto electrical installations, or it can be checked quite easily with -a voltmeter. If a cathode-ray oscillograph is on

hand, it is as well also to check the wave form of the vibrator system before final installation, but while the receiver is drawing normal )current. The .02mfd. condensers were right for the Ferguson 200 -volt transformer used in the original, but they may not be optimum for all makes. Don't be worried if there is a lot of hash while the vibrator is lying on the bench unshielded. That is What the case is intended to eliminate.

It is important to note that the condensers across the secondary are required to withstand a considerable peak voltage, so use the best mica condensers you can obtain. _ It you can manage to get the 2000 -volt type, the possibility of hreandawn will be remote.

The vibrator employed in the original receiver was the seven -pin Oak type 6513E7, and the connections have been drawn for it, Actually any ordinary synchronous type will do, provided the connections are modified to suit and

PAGE EIGHTEEN RADIO AND HOBBIES FOR DECEMBER, 1945

807-4 R.F.

4

i 888-4 1 Audio

the characteristics checked to see that wattage ratings are not exceeded.

It is worth noting that Ferrocart vibrators do not normally employ a separate driving contact, so that the "6V" connection Ls not necessary on the socket.

Referring to the circtilt again re- veals a rather complicated filter system in the low-tension supply line. There is very good reason for this.

Because of the ignition system and the various other electrical apparatus incorporated, a motor car is a notorious hot -spot of radio interference. Be- fore reception can be enjoyed, two main precautions have tó be observed:

Firstly, with the aid of suppressor resistors and condensers, the interference has to be minimised at the source. Secondly, the receiver has to be so constructed that no signal penetrates its circuits except that from the aerial mounted outside the car, where the interference level is not quite so bad. Hence the need for the substantial

metal case. Without this, interfering noises would penetrate every unshield-

,ed grid and plate circuit, so that the signals from the aerial would have to compete with noise voltages arriving by sundry other paths..

So our receiver has to be completely shut up against all random signal voltages.

Under these conditions, all leads entering or emerging from the case are potential signal -carriers, so that they either have to be thoroughly shielded or else bypassed at the point of entry into the case.

Figure S. Showing the general layout above and below the chassis of the original re-

ceiver.

Thus, ally lead. from the case to an external dial light must be completely shielded. Similarly for leads to an external loudspeaker or cables inter- connecting a multi -unit installation. Be quite sure that any unearthed wire entering your shielded case will carry interference voltages with it unless treated in this way.

Naturally, the most facile path for interference from the ignition system is the 6 -volt power lead, which actually connects the radio to the electric syster% of the car.

In the original model, the power lead enters the case at a point remote from the tuning coils and circuits. It is braided over the inch or so within the chassis and goes directly to the terminal of a 0.5 mfd can -type bypass condenser. This condenser is mounted in such a

way that its can substantially shields off the other components in the power lead filter circuit.

A .001 mfd. mica condenser, connected in parallel with the 0.5 mfd. unit, looks after any shortcomings of the latter,

LOW OHMS /CHOKE The low tension ,supply then passes

to a low resistance RF choke. These can be bought commercially, or can be made up by winding 20 or 30 turns of 20 -gauge wire (or thicker) on a small spool. The more turns the better; but keep the unit small and the d -c resistance low.

Thus "purged," the low tension lead can be taken away through shielded wire to the "off -on' switch, a n d thence back to another 0.5 mfd. bypass.

From this

Figure 6. Things are .:roweled be

nealh the chassis, but the placement of parts is orderly nevertheless. The filtering system is

tucked away in the upper right-

hand corner.

I CONSTRUCTION point a short lead is taken straight up through the chassis -into the vibrator box, and another goes through a second low -resistance RP choke, suitably bypassed, to the heater circuit. It is well to shield any long, exposed lengths of heater wiring, as interference can be radiated therefrom to other portions of the receiver.

Do not rely on the chassis to carry the filament return current, but run two leads right around the various sockets; connect the earthed one to the chassis at a point near the low tension filter circuits. In actual fact, a single common earth return Is desirable for the entire low tension circuit and filter. The whole thing is arranged to block

the outside interference at the point of entry into the ChasSls, ' What does get through is kept out of the high tension supply by the same network which keeps the vibrator hash in. And the heater circuit filtering is directed against either source of noise.

All this filtering and shielding may seem tedious, and is more than incorporated in some commercial auto sets. But it pays dividends when the time comes for installation in the car.

PERFORMANCE' ON TEST With the receiver operating on the

test bench, and not connected to earth in any way, the' shielding was such that only the faintest trace could be found of a very strong local broadcast station; and touching an aerial wire on either of the battery leads made no difference in level.

However, poking the end of the aerial through a hole in the case, or through the metallic speaker grille, brought to light all the locals at good strength. Similar rerailts could be achieved by sliding the shielding an inch or so back from the shielded aerial input lead.

The aerial lead, passing out of the case, must indeed be shielded right to the point of connection to the aerial outside the car. There is liable to be a big loss here, so keep the lead as short as possible, and use low capacitance cable for preference.

In the matter of capacitance, some microphone cable is good, but other


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PAGE TWENTY RADIO AND -lOBBIES FOR DECEMBER, 1945 ,

'RADIO THEORY

Perhaps no single phase of the radio art has . progressed, during recent years more than that involving apparatus ope rating at very high radio frequencies. What are now essentially wartime devel opments will gradually assume greater importance in civilian radio services, and it is well for servicemen and enthusiasts to gain some appreciation of the special problem involved in this part of the frequency spectrum. Here, then, is the first of a series of articles on this subject

written especially for "Radio & Hobbies" readers.

THE enormous contribution made by Radar to the winning of the

war is, itself, sufficient explanation for fhe abnormal activity on these very high radio frequencies. Radar will live on-and grow-as an essential peacetime service, but the lessons learned in its development will, be of untold value when television, facsimile and F.M. really get going.

Thus, the impetus of war has given a fillip to a very fascinating side of radio communication-if Radar can indeed be so categorised.

But quite apart from Radar, it was found vital to limit the weight of a great deal of the ordinary communication equipment used by the armed forces. Apart frpm the installations at various HQ's, so much of this gear had to be transported over the most difficult terrain by the Sig- nals Personnel themselves. Thus, the need for extreme portability often overshadowed other requirements.

The use of a very high frequency carrier simplified matters in this direction and small, highly efficient trans- ceivers were evolved, using a minimum of tubes, short -rod aerials, and yet giving splendid results.

Paradoxically, communication equipment used by the armed forces has, in some instances, to be specifically designed to limit the range and pattern of transmission; here again, very Short wavelengths came into their own. When we consider that an enemy may be lurking only a few hundred yards from the communication points, this equipment becomes less of a paradox.

To clear up the actual meaning of U.IitF., a standard nomen- clature of waves follows which has been developed in France and is intended for international adoption.

Below 30 Kc. Very low freq. (V.L.F.) 30 -300 Kc. Low freq. (L.F.) 300 -3000 Kc. Medium freq. (M.F.) 3 -30 Mc. High freq. (H.F.) 30 -300 Mc. Very high freq. (V.H.F.) 300 -3000 Mc. Decimeter waves, and 3000-30,000 Mc. Centimeter waves

(U.H.F.) The above table is culled from the

"Admiralty Handbook of Wireless Telegraphy" and can thus be regarded as authoritative. -In actuality, many frequency -band

By E. J. Goldsteen

groupings exist. Each nation has its own ideas and standards, but the range starting where the normal dual -wave radio receiver finishes (i.e., above 30 me/s) is often referred to somewhat loosely as "V.H.F." or "U.H.F.," with no mention of an upper limit. In truth, the term "high frequency" is a very relative one indeed!

Our friend the electrician spends his working hours among power lines at a frequency of perhaps 40-60 cycles. To this gentleman, a few cycles increment means that the frequency is higher than normal, and urgent adjustments are necessary at the power station; so off he goes to investigate what he now calls a "high -frequency power line," which might mean 65 cycles!

In the same way, we talk about t h e high -frequency response of an

audio amplifier; this despite the fact that it may not exceed 10Kc.I

And so to the ultra -short waves which have recently come to assume such prominence, demand- ing a radical departure from existing techniques and preconceived ideas. As far as this introductory article is concerned, we will consider mainly apparatus and application for frequencies of or higher than about 150-200 Mc/s.

H.F. "SKIN" EFFECT By way of a start, let us see how

these U.H.F. currents behave in practice. It is well known that, with increasing frequency, current tends to flow more and more on9 the outside of a circular solid conductor, which phenomena is called "Skin effect." So, for U.H.F., altogether different "wiring" methods must be used to couple the various circuits and stages.

In such apparatus one is confronted with a collection of hollow pipes called "wave guides" (because this is what they do). They take the place, more or less, of the familiar hook-up wire and tinned copper used in our wireless sets! Such "pipes" are colloquially referred to as "plumbing"!

It is necessary to realise that solid. copper busbar, of round or square section, is satisfactory for operation up to, say, 50 Mc/s, and the transition from solid to hollow conductors occurs gradually as the filquency increased beyond this. It could happen that a hollow guide may give improved operation at 50 Mc/s (or even slightly lower)

if used in a critical circuit-and so on. Possibly the closest medium to which

we are accustomed, and useable as an analogy to U.H.F., is light. Logic- ally, ft follows that, as radio waves approach the wavelength of light waves, they should behave in a similar fashion. It is equally important to avoid reflections and losses in the transmission paths between circuits.

BEAM TRANSMISSION Now, light may be focused into a

very narrow beam, as everyone who has ever owned a flashlight is aware; and so too can U.H.F. radio waves. Radar employs U.H.F. principally because of this property. The location of small targets, such as a distant aeroplane, is made practicable with this focused and highly directional- beam. For Radar application it is Obviously of no use to have in- discriminate wave propagation akin to that used by our broadcasting stations!

It is not proposed just here, to go into the technical details of Radar, which have , already been explained in this journal, but rather to give some idea of the techniques involved in U.H.F. practice. In passing, it is interesting to note that the Germans did employ a light beam which was modulated with voice frequencies, for field communication, but its use was subsequently abandoned.

,(Continued on Next Page)

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RADIO AND HOBBIES FOR DECEMBER, 19'5 PAGE TWENTY-ONE

RADIO THEORY

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Consider, for example, ordinary radio valves such as 6J8 -G, with its multi- plicity of electrodes and their attendant mutual capacitance effects. Such valves simply will not work at II.H.F. as the Impedance represented by even a few micro -micro -farads is appreciable. A frequency of 60 Mc/s can be regarded as the upper limit for conventional gear. How then, are D.H.F. currents handled and amplified?

And so comes perhaps the hardest part to grasp. tying in with magnification by the "Q" of a tuned circuit. U.H.F. currents are often amplified by a tuned circuit consisting of inductance and capacity (just as with a winding on an I.F. transformer) but reduced in form to possibly no more than a hole in a copper sphere or cylinder, instead of a coil of "Iitz" wire, tuned with a mica condenser.

As we all know, the short-wave coils on our existing receiver have only 6- 10 turns of heavy copper wire on a small former. Consider this reduced

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still further to one turn, and It becomes less difficult to imagine the same general function being fulfilled by the inner surface of a cylinder, or other hollow metal shape. From this emerges a new term for most of us- "cavity resonator."

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PAGE TWENTY-TWO

the importance of shape and dimep sien in these strangely tuned circuits. In truth, mechanical excellence becomes a criterion of performance at these very short wavelengths.

Our old friend "Q" factor-the ratio of reactance to resistance-is still the measure of circuit magnification and it 'may be a surprise to realise that, in these specialised circuits, a "Q" of many thousands may be achieved.

Oscillatory magnetic fields are readily produced in these resonators by an electron stream which is caused to pass through them.

Hollow wave guides of either square or round section may be made resonant at any desired ultra -high frequency. Just as a torch bulb, inserted at one end, would have its light re -


fleeted again and again, so also is the high frequency transmitted through a wave guide. The line of de- marcation between the wave guide and cavity resonators is indeed nut clearly defined.

Various expedients are employed to convert a U.H.F. signal to one more convenient for amplification (usually round 30 Mc/s) exactly as is done in the normal superheterodyne receiver. Certain special diode values function

well as mixers up to about 800 Mc/s, the signal and intermediate frequency circuits being in series, somewhat after the fashion of the old "autodyne" converter system. Above these frequencies, crystal detectors are possibly the answer.

A limiting factor for such work in normal valves is the "transit time effect," for the frequencies handled are such that complete alternations occur in intervals comparable to the electron transit time from cathode to plate. Modulation by the usual method is, therefore, impossible. Velocity modulation of the electron beam, as in Klystron and Magnetron tubes, gets over this trouble, but only for generating larger powers for transmission.

RECEIVER PROBLEM For receivers, the problem still

exists. _ But high transeonductance television pentodes such as 6AC7i1852. 6AB7/1853 are at least suitable for I,F. amplifiers at around 30 Mc/s.

Most of the gain at U.E.F. is derived from resonant circuits as outlined, and it must not be forgotten that an aerial, having a "Q" of many thousands, may be made resonant at any desired frequency or give a , gain up to 10,000 times.

The super -regenerative principle can be successfully used as a first detector at frequencies up to 224 Mc/s, with a U.H.F. triode valve designed basically like the old "30." but with much reduced interelectrode capacitance and physical dimensions. For those who are a trifle vague

about this matter of superregenera- tion, let us digress a little Briefly, a grid leak detector of more or less normal reaction type (as featured in many "Radio and Hobbies" designs for small radio receivers) is provided with enough regeneration to produce con stant oscillation. Advancing the re action control on a small set will pro duce this, and the whistling and gen eral behavior under these condition: ere well known.

However, in the superregenerativ( detector a "quench" voltage is introduced to the circuit in such a mannei as periodically to stop the oscillation This quench voltage may be derived from an external source, or supplied by the valve circuit itself; this latter is styled a "self -quenched" super regenerative detector.

The quench frequency is usually 01

the order of 20Kc and results in the. oscillatory detector being thrown in

and out of oscillation at this rate

Many fixed ideas have to be modified drastically in appreciating U.H.F. tech nique. Here is an illustration of in- ductive coupling-a coaxial cable to a

cavity resonator.

The net result is a tremendous increase in gain, for the detector is used in an oscillating condition, the quench voltage preventing audible beat notes

+overriding the signal. So much for that, except to warn

against such a method for broadcast reception. As the gain increases so does the valve noise-and how I With no signal tuned in (and even with) the noise is really something at broadcast band frequencies; besides which, the detector is hopelessly inselective and it radiates badly into the bargain. At U.H.F. and with special valves, one is much better off as regards noise, and the arrangement becomes completely practical

At wavelengths shorter, than 250

RADIO THEORY Mc/s, even the detector outlined above becomes useless and we are faced with the alternative of a crystal or chemical detector.

The problems of transmitters nave been simplified to some extent, as special valves have been developed which deliver considerable power as H.F. oscillators at wavelengths as short as 1 centimetre (300,000 Mc/s), And it only remains to couple this to a radiator in order to transmit the signal.

These radiators, or aerials, are of the rod type and made with their length a definite function of the wavelength. Can you conceive a piece of copper rod about six inches long or less transmitting several thousand watts of R.F. power? Yet this is a fact!.

It is hoped that the foregoing has served its purpose as a general introduction to U.H.F. In following Issues it is intended to discuss transmitters, receivers, and aerial systems for operation on ultra -high frequencies. But one can only hope to present a general picture of it all in a few columns. In truth, many, many thick books have been written on "wave guides" alone.

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RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE TWENTY-THREE

RADIO THEORY

A COURSE IN RADIO TRANSMITTERS Scores of readers just now are keen to gain the Amateur Proficiency Certificate. Many others just wont to know how

transmitters operate; how they differ in principle from the more familiar receiving equipment. Timely, then, is this special series of articles, prepared expressly for "Radio Ir Hobbies" by the technical staff of the Australian Radio College.

Instruction Paper Number L

THERE is an undoubted thrill in

the idea of sending one's voice half -way round the World. But, just at present, it can't legally be sent across the street without the sender conforming to certain licensing requirements. And not the least of these is a knowledge of transmission theory and practice.

It is not proposed here to discuss the routine of obtaining an amateur transmitting licence-that information has already been given-but to tell you something of the underlying principles and theory of radio transmission.

The electromagnetic waves which constitute a radio transmission are transverse disturbances of an elastic medium;, that is, the direction of movement of the medium is at right angles to the direction of wave propagation.

The medium, which, for want of a

better name, is termed ether, is considered to permeate all space without having any material properties. The assumption of such an all-pervading medium allows a reasonable scientific explanation of the fact that a vacuum, which is space in the truest sense of the word, will still support electromagnetic waves.

The first premeditated radio transmissions were carried out during 1887 -

Al A2

But when a condenser is discharged suddenly through a path of very low resistance, the potential difference between its plates is not immediately neutralised by a single uni -directional movement of electrons from negative to positive; even if no coil is present. there will be a small amount of inductance in the connecting wires! Some of the electrons overshoot the mark, to put it crudely, and what was previously the positively charged plate acquires a surplus of 'electrons.

Again the condenser will discharge, but, once more, this electrical inertia effect will cause some electrons to go

farther than they should, and the condenser will be forced to discharge again. Each charge is smaller than the

one preceding it, because some of the energy is dissipated by the resistive lasses of the plates and connecting wires.

The discharging condenser, then, far from producing a single pulse of direct current, promotes a flow of alternating current of substantially constant frequency but of diminishing strength or amplitude. Diagramatically the effect is as figure 2.

When the plates of a condenser are

proximately 500 megacycles. Hertz even demonstrated that his electromagnetic waves could be reflected by metallic objects.

Between 1888 and 1895 new developments were largely on the reception side. Most notable was the invention of the coherer detector, in 1894, by Edouard Branley.

In 1895 the world first heard the name of Marconi, when this then 22 - year -old young man succeeded in transmitting and receiving signals over a distance of 1} miles. Thereafter the world rarely had a chance to forget the name of Marconi, because he fol -

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lowed improvement with improvement, always reaching out to greater distances. First tens of miles, then hun- dreds of miles.

With all this early work by Marconi and his contemporaries, spark transmitters were the rule, greatly improved, of course, from the apparatus used by Hertz. In fact, this type of transmitter was still in general commercial use long after the invention of the three -electrode thermionic valve.

It was not until 1919 that the first valve transmitters were introduced to this country, and 1925 before they replaced spark transmitters in coast stations. Their adoption in ship In- stallations came even later, in 1928-29.

MANY DISADVANTAGES Spark transmission bee many dis-

advantages, chief of which are waste- fulness of power and short range corn - ..n rnA In ,,n..H....n..c n,uvn enne

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FIG. I.

1888 by Heinrich Hertz. Figure 1 indicates the type of apparatus he used for his experiments, Essentially, it consisted of two metal rods, each ter- minating at one end in a large capa- citor plate (A), with a spark gap (B) formed by the other ends of the rods. A high potential difference is applied between the plates so that on Al. a positive charge appears, and on A2 a negative chargé.

If the width of the spark gap is adjusted so that, when the plates have been charged to their maximum degree, the potential difference across the gap is sufficient, to break down its insulation, electrons will move from A2 to Al, thus destroying the state of un- balance created by the initial charge.

close together, energy is cormnea ar most entirely to the circuit in which it is evident; but, if the plates are very widely spaced, some of the energy will be radiated in the form of electromagnetic waves. The physical processes attendant upon radiation need not worry you at this stage. They will be discussed fully in a later article dealing with wave propagation.

Hertz's apparatus conformed to the widely -spaced plate condition, and he had thus constructed the first spark transmitter. He had also devised the first ultra high frequency transmitter.

So you see it is perfectly true that there is nothing new under the sun. Here we are, almost 60 years later, working with radar equipment on a part of the frequency spectrum near that occupied by the early transmissions of Hertz-on a frequency of ap-

High peak voltages necessitate extremely high insulation of all parts, and severe interference is caused hi neigh- boring receiving apparatus during operation.

The last-mentioned is probably the most serious drawback. It eventually led to the complete banning of all spark transmitters, except in ship installations. and even here their use is allowed only in cases of extreme emer- gency when all other methods of transmission have failed. Nevertheless, it is desirable that applicants for an amateur transmitting licence should know how a spark transmitter operates.

Figures 3 and 4 illustrate two types of spark transmitter. The first shows the aerial as an actual part of the oscillatory circuit, In the second case the aerial is loosely coupled to that

PAGE TWENTY-FOUR RADIO AND HOBBIES FOR DECEMBER, 1945

RADIO THEORY part of the apparatus which produces the high frequency oscillations. In figure 3 the capacity in the circuit is the aerial -earth system (indicated by dotted line). In figure 4 a fixed condenser of known capacity Is used, while tuning is carried out by Varying the inductance of Ll and L4.

The power supply of figure 3 Is an induction coil which may produce, perhaps, a peak voltage of 10.000 volts. An induction coil is a device which enables one to convert low voltage d.c. (from a battery, for Instance) to high voltage o.c. Most modern cars employ an induction coil to provide the necessary voltage to energise the motor spark plugs.

MODE OF OPERATION The operation of the transmitter de-

picted In figure 3 is very simple. When the key is closed, current flows from the battery through the primary winding of the coil and magnetises the iron core, on which both coils are wounds The magnetised core attracts a springy blade located at one end of the coil, as shown in the sketch. In moving towards the magnetised core, the blade, which is really one contact of the switch (S), breaks the primary circuit.

Here is the important part of the process. The magnetic lines of force which "grew" out of the primary coil when the key was first closed, col- lapse suddenly as the primary circuit is broken. In so doing, they pass through the secondary winding and generate a high voltage, partly because the secondary winding has many more turns of wire than the primary, and partly because of the greater speed with which lines of force move through the secondary winding.

For the latter reason the voltage induced in the secondary is much greater when the primary circuit breaks than when it makes, because the growth of

FIG. 4.

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the magnetic field surrounding the primary is. slower than its decay.

Circuit constants are arranged so that each time the primary winding is opened, the voltage across the aerial - earth system will be high enough to cause a breakdown of the spark gap insulation. The sudden release of the charge between aerial and earth sets up an oscillatory current, with conse- quent radiation of energy.

With the breaking of the primary circuit, the iron ceases to have any magnetic attraction for the springy switch blade. Consequently, it flies back against the contact (C), and com- pletes the primary circuit once more. Again the core is magnetised. and the



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PAGE TWENTY-FIVE

RADIO THEORY

RADIO TRAMS« TTEES -Continued previously detailed cycle oI operations is repeated; and it continues for as long as the key is depressed.

The spark discharge across the gap is maintained until the voltage between aerial and earth falls below the critical value necessary to maintain ionisation of the air in the gap. Be- cause the spark gap offers consider-

able resistance to an oscillatory current, the critical extinguishing voltage is reached fairly rapidly, especially since the resistance of the gap increases greatly as the current decreases.

The effect of all this is that, even though the vibrating portion of the induction coil may move rapidly enough to produce 500 sparks per second, in actual practice each spark endures for much less than one five -hundredth of a second. A more likely figure is one hundred thousandth of a second. The result is a train of heavily -damped oscillations, as in figure 5.

A heavily -damped wave train, as de- picted, tends to shock the aerial into oscillation over a broad band of frequencies, rather than at one frequency only. Such shock effect may be, minimised, however, by using the circuit arrangement of figure 4.

The aerial is loosely coupled to the oscillatory circuit, rather than directly connected to it. Although conditions in the oscillatory circuit are still con- ducive to heavy damping, the losses in the aerial circuit are reduced, and are of substantially constant value. The oscillations induced in the aerial - earth system, therefore, persist for a slightly longer period than when the circuit of figure 3 is used.

FIG. 6.

A diagramatic representation of what occurs with a correctly -coupled aerial circuit is shown by figure 6. The terms primary and secondary refer to the primary and secondary windings of the aerial coupling transformer in figure 4.

It will be seen that there is less shock effect and so less tendency for the transmitter to occupy an unduly wide frequency band. The power supply shown in figure 4 is an alternator, for an induction coil is useless when high power is required.

But the use of high power with spark transmitters introduces a complication, in that it becomes difficult to ex- tinguish the spark rapidly enough to follow normal keying of the primary winding of the step-up transformer be -

tureen alternator and spark gap. This is due to the greater heat generated by the spark causing some of the electrode metal to volatilise and thus form a semi -permanent conductive path across the gap.

Several methods are used to overcome this problem, chief of which are the use of a rotary spark gap and/or

a blast of air directed at the gap. The first method keeps the electrodes cooler by virtue of the fact that consecutive sparking does not occur between the same points, The second method literally blows out the spark.

Another type of transmitter used extensively in the days before the thermionic valve, and, to a lesser degree after, was the arc. A simple ofrcuit of an oscillating arc is shown by Fig. 7, while a close-up of the arc Itself appears in Fig. 8.

The operation of this type of oscillator depends upon the fact that an arc has a negative resistance characteristic. In other words, the potential difference across the arc becomes

greater as the oscillatory current flow- ing through it decreases, a directly opposite effect to that obtained with an ordinary resistance.

By placing the arc in series with a tuned oscillatory circuit, the effect can be put to good use. If the spark gap is adjusted so that its negative resistance just balances the positive resistance of the coil and condenser all losses in the circuit will be eliminated and it will oscillate continuously.

For best results overheating of the arc must be avoided. The precautions adopted to guard against excessive heat are: (1) The arc is burned in a strong transverse magnetic field. (2) The arc is enclosed in a metal chamber which is kept filled with a hydro- carbon gas, coal gas for instance, because of its superior heat conduction properties. (3) The carbon anode is replaced with a water-cooled copper electrode. (4) The cathode, which is of carbon, is slowly rotated during the operation of the arc.

All the features mentioned are clearly visible in Fig. 8 The strength of the magnetic - field used in the arc chamber depends upon the power of the transmitter and maybe anything between 2000 and 20,000 gausses The lower figure would be about equal to the field strength of a 5 -inch dynamic speaker, while the higher one would represent the field strength of a large theatre type reproducer,.

A major disadvantage arises out at

the method of hying employed with this type of transmitter The arc must be kept burning continuously during the transmission, tor it cannot be started and stopped instantaneously. It is usual, therefore, to arrange that depression of the signalling key short circuits portion of the aerial inductance.

As a result, the transmitter radiates two frequencies, one when the key is depressed and another when it is released. The two radia- tions are known respectively as the marking and spacing Waves Each arc transmitter thus occupies two frequency spots, which is not at all desirable.

H.F. ALTERNATOR The final non-thermionic method

of transmission worthy of mention is the high frequency alternator. Prob- ably the best known instrument of

this type is the Alexanderson in- ductor alternator. In construction, It does not follow orthodox design. Both field and armature coils are station- ary, whereas with the ordinary low frequency alternator used in the generation of A -C power, either armature or field coils rotate.

With the Alexanderson alternator the field and armature coils are as- sembled on a circular frame A cross- sectional view of the frame is shown in Fig. 9. At intervals around the inside of the frame, pole -pieces upon which the armature coils are wound, form a small air gap in which a thin disc of iron rotates. The periphery

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of the disc is slotted. the slots being filled with gunmetal.

Gunmetal is a non-magnetic material and, consequently, as the disc is rotated, the gap. between successive poles is alternately filled with iron and gunmetal. When the gap contains iron the magnetic flux density in it increases, but, when it contains gunmetal, the flux density decreases.

The rapid increase and decrease in flux density causes the generation of an E.M.F. in the armature coils. As the coils are connected in series, the output voltage of the machine is the sum of the voltages generated in each coil.

The frequency of the voltage gener-

PAGE TWENTY-SIX RADIO AND HOBBIES FOR DECEMBER, 1945

RADIO THEORY ated depends upon the number of poles used and the speed of the iron disc. As an example, an alternator designed to generate voltage as 27,200 c.ps. would require to rotate at 2675 r.p.m, if there were 1220 poles. Alternators of

the type described can be produced to generate voltages at a frequency of 200,000 cycles per second; however, the expense of manufacture is extremely high for frequencies of this order.

The next article in this series will deal with the introduction of the thermionic valve, with a brief history of its development.

I AUTO RECEIVER I

. (Continued from Page 19)

cable is worse than ordinary shielded wire, The large '"- sin-'- `rand cable used in some noise -reducing aerial systems is quite good, but a short length of coaxial cable would be best of all.

Despite the obviously high sensitivity, vibrator hash was below the level of valve noise, &c. But earthing the tuning gang or the vibrator case.to the chassis at various spots with a screw driver brought the hash up beyond a tolerable limit, illustrating the value of one -point earthing under these conditions.

When ultimately installed in a typical sedan car, the ignition noise was audible only behind the weakest local stations while driving in the suburbs. This was before any spark plug suppressors had been fitted tc the car, although a 0.5mfd. condenser was wired betw$en the ammeter and frame. And the car is one rather notorious for noise!

Obviously, /the preliminary precautions on shielding and filtering had conferred a big start in the war against car noise.

So much, then, for the construction of a car radio. It you still feel un- daunted by the prospect of much hard work, go to it. But read this article very carefully and extract all the information you can from its neces,arily condensed paragraphs.

In a later issue we will have something to say about the problems of installation,

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RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE TWENTY-SEVEN

RADIO THEORY

' II " 'I Passing on in our study of valve types, we come this month to a brief discussion of the pentode and its more recent "stablemate" the beam -power tube. The following article tells how the pentode came to be developed and something of

its operating characteristics in actual service.

I T is probably not an exaggera- tion to say that pentode valves

are the most widely used of all types today.

As we saw last month, the tetrode valve structure solved the chief difficulties in connection with the design of R.F. amplifier stages.

However, it soon became evident that the screen grid itself produced certain difficulties, as well as con- ferring the stated advantages. In fact, the whole story of valve development gives the general impression of more and more "bits" being added to compensate previous additions.

The outstanding limitation of the tetrode structure hinges on the so- called "secondary emission" effect. Electrons travelling outwards at high speed from the cathode strike the positive plate with considerable velocity. In fact, the energy of the moving electrons is such that they are liable to pentrate the molecular ritrvuture of the plate and dislodge éteciirons already there.

current and decrease the plate current.

Provided the plate voltage can be maintained at all times at a figure substantially higher than the screen voltage, the effects of secondary emission are not troublesome, since the attraction of the plate for the freed electrons is ever so much greater than that of the screen. However, this takes no account of the conditions which hold in actual service.

We have already seen that, when a valve. Is employed as an amplifier, there is a substantial variation in the instantaneous plate voltage, corresponding to the variations in output signal voltage developed across the plate load. When the valve is handling large signals, the plate voltage can swing downwards to instantaneous values which are comparable to, or even less than the steady screen potential.

Thus the problem is not so much one which concerns the Initial operating voltages, but

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In everyday language one may say that the moving electrons which strike the plate "bounce" other electrons right away from the parent material. In a triode this leads to no obvious

ill effects. The plate is the only positively charged body in the structure and the dislodged electrons are immediately attracted back to it, so that there is no lasting effect on the plate potential.

In tetrodes, however, things ate quite different. The positively charged screen is now present and some of the electrons freed by secondary emission from the plate become attracted to trie screen. This reverse movement of electrons from plate to screen naturally tends to increase the screen

etc -1H.

Figure 1. A plate family of curves for type 24-A, a typical R.F. amplifier tetrode. Note the erratic behavior of the plate current for plate voltages less than about 90. This is due to secondary emission to

the screen.

rather the instantaneous conditions which apply when the valve is handling a large input and output signal. In actual fact,. the urgency of the

matter would have been less apparent had the tetrode structure been applied only to R.F. amplifier valves for, in most cases, R.F. amplifier stages are called upon to handle only a relatively small signal voltage amplitude.

It s happened, however, that valve designers were alive to the possibilities of the tetrode structure for audio voltage and power afnplil'ication. While tPie triode had certain admittced advantages for this work, the tetrode structure held promise of higher gain and efficiency.

Tetrodes were thus being developed and applied for audio work, where

large signal amplitude is commonplace and where secondary emission effects therefore compromised some of the advantages sought.

The secondary emission effect is best understood by referring to an actual case, and the well-known type 24-A R.F. tetrode is as good an example as any. The plate family of curves is illustrated in figure 1.

It will be seen that the curves are drawn for a screen voltage of 90, which is normal for that particular valve type. Referring to the zero -bias curve (marked "Control Grid Volts Eel= 0"), the plate current is seen to reach an initial peak of just under 3 milli - amps at some very low plate voltage- something like 10 volts.

SECONDARY EMISSION With such a low voltage, velocity of

electrons approaching the plate is small, and so ìs the resultant secondary emission effect. But, as the plate voltage is increased, the plate current takes an unexpected dip; at the same time the screen current (curve marked "Ic2") rises noticeably.

Very obviously, in this region, the rise in the reverse plate -to -screen current due to secondary emission is actually greater than the natural rise in plate current with increasing plate voltage.

At a plate voltage of about plus 60 the effect reaches its peak, but, above that again, the plate current begins to behave In more nortnal fashion. The characteristic does not actually straighten out until the plate voltage exceeds the screen voltage.

It is interesting to note, in passing, that for plate voltages between about plus 10 and plus 60 the valve exhibits a negative plate resistance effect, the plate current decreasing as the value of the applied plate voltage is increased. This novel effect has been utilised in the so-called Dynatron or negative resistance oscillator, but the property is poor compensation for sacrificed efficiency,

What is more important to the designers of ordinary equipment is that a big section of the curves is branded with the words "values unstable." As might be imagined, valve design-

ers were not long in evolving methods to minimise Or overcome the difficulty. The less successful methods involved coating the anode surface with a material to retard secondary emission, and a juggling with the geometry of the electrodes, or the applied operating voltages.

But the method which was widely used in practice was the addition of another grid between the plate and the screen. This employed a very open mesh and was usually operated at the same potential as the cathode. The addition of the third grid produced a five -electrode valve, which gave rise

PAGE TWENTY-EIGHT RADIO AND HOBBIES FOR DECEMBER, 1945

RADIO THEORY to the term "pentode" or "penthode."

The pentode structure is illustrated in figure 2. Electrons move outwards from the cathode at a velocity de- pendent on the retarding influence of the negative control grid and the attraction of the positively charged screen.

Approaching the screen, they are further attracted by the plate and pass on to it through the open mesh of the "suppressor" grid, as it is called. Be- cause of their high velocity, the electrons are not greatly affected by the presence of this extra grid.

Cathode) id

8oreen' lAtioppreeaor

Plate

Figure 2. The suppressor grid in a pentode is located between the screen and plate and generally connected to the cathode, either internally or at

the socket.

On striking the plate, the usual secondary emission effect is evident and freed electrons are propelled in- wards from the plate surface. How- ever, their velocity is relatively small and they are turned back or repelled by the suppressor grid, which is at the same potential as the cathode, and therefore negative with respect to either plate or screen. A very satisfactory solution to the problem!

The same construction a n d effect is .utilised in all pentodes, whether they are

Figure 3. Illus- trating the electrode structure of a modern beam power output valve. Note that the electron stream is beamed both vertically a n d

horizontally.

BEAM - FOAMING PLATE

CAT NODE

GRID SCREEN

of the small RF amplifier type, power output pentodes, or the much larger varieties used for transmitting purposes. Naturally, the physical size, spacing and mesh of the grids is varied to obtain desired electrical characteristics.

In more recent years, the secondary emission problem has been approached from another angle, as illustrated in figure 3. In this, the general design of the electrode structure is changed to restrict the electron flow into two defined brains, instead of a general radial Bow outward in all directions from a eirettlar cathode. To achieve the desired results, the

cathode sleeve is made oval and the large grid side -rods positioned directly

opposite the sharply -curved surfaces. Outside the screen again, two beam - forming plates, connected internally to cathode, are mounted, which leave only a restricted path for the electrons.

The turns of the screen are lined exactly behind corresponding turns on the control grid, so that a beam effect is achieved in a vertical as well as a horizontal sense.

The actual plate is located at a distance from the other electrodes such that the individual beams merge into a shower of electrons immediately in front of the plate surface.

The general effect is to reduce considerably the velocity of electrons striking the surface of the plate. Fur- thermore, the thick "shower" of slow - moving electrons approaching the plate has a strong repellent effect on secondary electrons.

Alignment of the screen and control grid turns keeps the screen current down below that of a comparable pentode, and various other refinements have contributed to making the modern "Beam Power" valve a very efficient one indeed. Well-known examples of this type are the 6V6 and 6L6.

Compared to the curves for an ordinary tetrode, the plate family of a pentode, or beam -power valve looks very orderly, by reason of the suppression of secondary emission effects. Curves for the 6V6 -G, at a screen voltage of 225 are shown in figure 4.

The radically different shape, as

.

PEATE

compared to a triode is immediately evident. Plate current rises steeply up to a plate potential of about 25; then there is a definite "knee," beyond which the curves flatten off, showing iittle increase in plate current for a very big change in plate voltage.

To obtain maximum efficiency from a pentode or beam tetrode output valve the load is selected which puts the load line through the "knee" of the zero bias curve.

The load line shown in figure 4 re- prr,rrils a load resistance of .las( over 1)000 nnnts, derived with cooveraion facuur curves front the ordinary 2; 0 - voll cuncli(ions. General operating conditions arrived at on this basis are as follows: Plaie and screen voltage.


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RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE TWENTY-NINE

RADIO THEORY

A "MUST" in EVERY RADIO SERVICE KIT

CALSTAN Model 51 1 AC -DC

MULTIMETER and OUTPUT METER

A Sturdy dependable instrument combining the features of both Multimeter and Output Meter. Built in an attractive portable case and guaranteed to operate with a high degree of accuracy. No serviceman is fully equipped without one.

Voltage Ranges. A.C. Output, and D.C. 0-10; 0-50; 0-250; 0.1000.

so Current Ranges. 0-I; 0.10; 0-50; 0-250 M.A. Resistance Ranges. 0-5000; 0.50,000, 0-500,000 ohms.

EXPERT REPAIRS Zenith announces a new Repair De- partment where all adjustments rind repairs to graphic recording, standard and substandard electrical instru- ments will be undertaken. Repairs are effected by an expert with .15

years of English. Continental and Australian experience.

ZENITH RADIO COY. PTY. LTD.

131-133 Palmer Street (off William Street), Sydney.

FA 2157.

225; grid ,, las, -11.25; plate current, 38.2 milliamps; screen current, 3.8 milliamps; power output, 3.5 watts.

Inspection of the load line shows that, for a grid swing of from 0 to -22.5 volts. a very big range in instantaneous plate voltage is achieved, Not much space on the curves is "wasted" to the left of the zero -bias line, while the peak positive swing approaches fairly closely to twice the applied plate voltage.

At the same time there is a substantial variation in plate current, and this all adds up to a high power output.

Further to illustrate the point, the

Under ordinary condition's, this means a saving of better than 15 milli - amps in average high-tension current, and a 60 -volt reduction in the voltage required and applied across the various filter and byt}ass condensers. Con- sidering, also, the increased sensitivity, it is little wonder that set,manufacturers have swung almóst exclusively to the use of pentodes or beam tetrodes in power stages.

Unfortunately, our story does not end on this happy note, for the pentode and tetrode have inherent limi- tations as power amplifiers, especially when operating into a loudspeaker as output load.

200 300 400 PLATE (Eh VOLTS.

Figure 4. Curves for th with a screen voltag of 225; th load lin is

for this voltag. The dotted curve is the zero bias lin for a 2A3, which has boon added for th sake of comparison.

dotted line has been added, which shows the zero bias curve for a .2A3 triode. In terms of ordinary class A amplification, the presence of the "knee" in the curve of the beam - power valve (or pentode, as the case 'may be) obviously makes possible the generation of a greater plate voltage across the output load, suggesting greater power output,

It is courting inaccuracy merely to look at curves without analysing them completely, but the above observations are easily substantiated by reference to published data.

To obtain a power output of .3.5 watts from a single 2A3 one has to provide a high-tension voltage of 250, plus 45 volts bias. The current is 60 milliamps, so that the total input wattage is 17 7 watts. This yields an overall efficiency figure of just under 20 per cent., and a signal input of 45 volts peak is necessary to produce the full rated power output.

Let us see the requirements of a 6V6 -G for the same power output. One needs a plate and screen voltage of 225, plus a bias of 11.25. The plate and screen currents are respectively 38.2 and 3.8 milliamps, rising on full output to 40 and 5.9 (approx.) milli - amps.

Taking these higher figures, the input wattage works out at 11.1 watts. Thus, the overall efficiency is better I.han 31 per cent, and a peak signal input of only 11 volts is required for full power output,

Referring again to figure 4, it is not hard to imagine that a departure from the stated load resistance value will radically upset the nicest calculations-and that is precisely what happens in practice. The load presented by an ordinary loudspeaker varies enormously with frequency and this produces considerable distortion; far more, in fact, than that experi- enced with a triode under the same conditions.

Another point is that the stage is unable to provide any worthwhile electrical damping on the loudspeaker diaphragm, which tends to vibrate of its own accord, even after a driving impulse has éeased.

These and other effects, which have been examined in more detail in recent amplifier articles, have, earned the pentode a bad name among quality enthusiasts. Many use only triodes for this reason, but the modern trend is to employ pentodes or beam valves for their high efficiency, correcting their defects with the aid of negative feedback.

All that has to do with power output stages, but there is no reason to assume that a pentode is always a cheap and nasty valve. As a résist- ance -coupled voltage amplifier, where conditions are constant and predict- able, a pentode will give far more gain and better fidelity than a triode.

And, as RF or IF amplifiers, pentodes are used almost exclusively.

PAGE THIRTY RADIO AND HOBBIES FOR DECEMBER, 1945

TRADE REVIEW

I

I

This month we introduce again a feature which has naturally been curtailed during the past two or three years-our Trade Notes. From month to month we will describe new products which come to our notice, and old ones which are making

a welcome reappearance on the market.

Radïotron Twin-trïode The A.W. Valve Co. announces that it is now

manufacturing locally the twin -triode type 6SN7- GT. Each section is identical electrically with the 6J5 -GT.

Having independent cathodes, the two sections may be used in push-pull or parellel operation, or as separate stages in an amplifier. Use as a mixer is yet another interesting possibility for this useful valve. Overall size is approximately 3tin. x lain.

Complete characteristics are available on application to the A. W. Valve Co. at 47 York -street, Sydney. typically, as a class A amplifier, each section of the

6SN7-GT draws 9 milliamps with a plate voltage of

250 and a bias of -8.0. Plate resistance is 7700 ohms,

transconductance 2600 and amplification factor 20.

i R.C.S. PARTS COMING BACK After having been very scarce during the war years, RCS

components are now reappearing on the market in greater quantities, and home -builder's requirements will soon be met

in full. OF particular interest to amateur

set builders will be the increasing stocks of the RCS DA -7 dial kit, which was adopted as standard for the "Radio and Hobbies" "Little General" series of

receivers, as well as for other small sets using the "H" type tuning gang.

4

i

Ample stocks are also available of

RCS high-tension filter chokes, the type illustrated being rated to carry loads of up to 75 milliamps. On the same standard core and mounting, RCS provide a low d -c resistance filter choke for vibrator -powered receivers which incorporate directly -heated valves.

Companion to t h e iron -cored filament choke is the RCS low-tension RF choke for vibrator - powered receivers, wound ,

on a moulded Trol bobbin. D -c resistance is given as 0.1 ohm.

I

FERGUSON TRANSFORMERS ACOMPARATIVELY new name in

the radio trade is that of Fer- guson's Radio, of McMahon -street, Willoughby, NSW. During the war they have specialised in the production of transformers for radar and general communication equipment.

Their products include audio, output, power a n d vibrator t r a n s formers, also low and high tension filter chokes. Nor- mal finish is with pressed metal side plates for vertical mounting, and they are available in standard designs or to meet individual specifications.

Ferguson's Radio are also developing a line of test equipment for general laboratory work. Phone JA6177.

COMMUNICATION

RECEIVERS Small Number

Brand New In original Tropic Proof Carton

and Case

PHILIPS TYPE R163 Continuous Coverage

0.55 to 22 m.c.

Direct reading calibration. Oper- ates from A.C. Voltages 110, 220,

240 and 260 volts.

IDEAL FOR RADIO. "HAM"

Manufacturer's Fixed Price £65 inc. Sales Tax.

Concessionaire:

L. J. KEAST 23 Honiton Av.

W. Carlingford, N.S.W. 'Phone, Epping 2511.

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE THIRTY-ONE

Mr. Murrell, of Cul - cairn, NSW, saw this idea for a combined amplifier and mixer stage in an American technical journal. He tried it out and reports that results are excellent on

both channels.

PAGE THIRTY-TWO

iuuuspedKer output transformer and its voice coil, and in- stalling two independent switches and an additional output transformer, as indicated in the sketch.

The method avoids the necessity for disturbing the wiring of the receiver chassis, gives complete isolation of the headphones and allows headphones and loudspeaker to be used independently or together, as desired. Also, the method allows old style magnetic or horn loudspeakers to be employed as extension loudspeakers.

Exishn,g Spkr, Trn ns.

Voice ., Extra Cott bans, 10,000 (OpPionnl )

Indepen- don / S.p-D.T.

+ . swifiheb.

teeing level, is optional. Almost any serviceable loudspeaker

transformer will serve to feed the phones. The voice coil winding (thick wire) is connected to the switches, while the normal primary (many turns of fine wire) connects to the phones.


BEGINNERS

Gadgets and circuits which we have not actually tried out, but published for the general interest

of beginners and experimenters.

Vacuum -Tube Voltmeter Circuit HEfBE is ail interesting circuit

for those who like experimenting with simple test equipment-a general purpose valve voltmeter.

Mr. Horsnell, of Matrickvllle, writes: "I am enclosing a circuit which you may recognise as being basically similar to the Vacuum Tube Volt- meter in 'R. and H.' for August, 1945. It was the very thing I had been waiting for, although I did not care for the unusual voltage ranges.' +

"I decided to try and make it up to the more usual 10, 50, 250 and 500 volt ranges and also to increase the input impedance. And, for another thing, I wanted to make it up as a separate unit, so I In- corporated its own power supply on the chassis, After a little juggling, I found that, by removing the 75,000 ohm resistor, In the balanc- ing network, I could get the desired range easily

"It was found desirable to reverse the function of the Calibration and Zero adjustments on my job, and the changed conditions are indicated

0005 Hn O1

10ryß,

AMPLIFIER -MIXER 6R8 -G

on the diagram. A switch provides for D -C. Audio or R.F. input.

"I found that the plate supply voltage was by no means critical; the circuit actually worked OK with anything from 45 to 250 volts Input, so I

left it at 45 to save the tube R.F from doing unnecessary work.

Sensitivity was unaffected."

n -c 677-

F6

0.2

0a

5000 Cal. Adj.

zero Set 15000

B+ 43 to 250

Connecting CIRCUMSTANCES often arise

which make it desirable to use the domestic receiver with ear- phones instead of the loudspeaker. An article on this subject was given in the April 1943 issue of "Radio & Hobbies," bui further notes are supplied by Mr. Howard of Chelten- ham, NSW.

The method suggested by Mr. How- ard involves breaking the connections between the main

RESISTOR AS A WINDING FORMER

IF you have occasion to wind up a resistance of a few ohms, there is

no need to waste time searching for a suitable mounting. Take an ordinary 1 -watt carbon resistor, wind on the required number of turns, and connect the ends directly to the re-

sistor pigtails. The carbon element of several thousands or millions of ohms, In parallel with the few ohms in the wire, will not make any appreciable difference to its value.

Clean the resistance wire thoroughly, make one or more small loops where it is to be soldered, and embed these in a smooth blob of solder. This will prevent the wire coming loose and ensure more permanent contact.

Phones to Your Set Two independent single - pole

double -throw switches are required, their exact nature being unimportant, as there is no high voltage in the switched circuit. According to their relative positions, either the phones or the main loudspeaker are on, both may be on together, or both off. The potentiometer which shorts out the phones, and therefore limits the lis-

Spkw .

Artificial Rock IC'anlnued feint Pee a)

)n ;re an):<e.l hardening of cement. One method. which 'r aid to be et. (eetive. Y the spaying Of the metes o1 the cement with aheale of antla or Common water pass (this te the

sterol used for prasrrins App when you can get bur).

The[ Ya one serious ddealtage el concrete te lie Comparltleity ana:: teem. strength when tined wIthou'. reinforcement. It resla4 cornpesabr but give way nder tendon. For- tunately this has been mettem* by the use of tlnlertult roda of Fob and steel mesh. This addition mates of concrete one of Um mat useful bed - mg mmertab.

Concrete and aged make a wonder - tut Canbnatien. They hove remarkable adherent properties :or ear, other and are Meet In their enloo .!lore undo hat. Tetay ate almost bnm.:uc lrrom ea atetph rle iltec : knees 4

ntherin[ and the metal embedded In the Moore. Is peeteried !ma: nor - talon. Melted of deteriorating with age. reinforced concrete Improved he tenure during the whole period ol les existence. It Y easier and quicker to tote than stone or brickwork. le

o al- mlt eamp-peool and ere -proof and

any dates stranger. We hats Just begun to male the

enormous advantages 01 concrete In mworld which expenenng an mute punIng shasa

to a leee and the l bolds

Meth promue for Um versatile maierial.

'The woe bee laugh( tin many lessons in me of and this will be f treat benefit donna the Timm ehr ad when strenuous ellore must be made tO replace the emes M Manta that have been destroyed

by war.

BATS LEAD TO RADAR TH. secrets of how bate taught In-

secte. and avoided oastiel. In fat dar, mntubuted 10 the eneovery of Rader principles.

For 10 Yard. Neese Hamilton Haetrldge. 11 -year -old physiologist. wendered snout the bets afore he found tige Grimer.

Prefeue 1 Hamilton .yr. that bam have a .ehenitkno And teeing tec

aller than Inut more and mo !Melted then the beat Radar let.

'my Hat lue ben wbel. I dt. covered In.t deal line demo beta bumped Into things. sot Blinn bet flint ^yrnblu.nr I dtaeovered mate ny-

Ino bel pllala ngee noie

Weil be Iran IM veMM ne e

beam of wine lntellung lasse than sound.

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large an -Pecan tire echoes. be4 mn dew

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RADIO ANO 0015105 FOR OECFMNR. lee[ CAGE It' RÎTNREII

DX NOTES

BROADCAST &ANDD.X Despite the increasing volume of static, as summer approaches, many interesting signals from overseas stations have been received in recent weeks on the broadcast band. Already, the Allies are making their presence felt on the Asiatic continent, and several transmitters arc reported from Japan itself.

" D ADIO & HOBBIES" has received an interesting letter from

Geoff Hodson, 3rd radio officer at Singapore radio, containing information he believed may be of interest to readers.

Two meth programmes are handled by this service: The national programme, consisting of native and English language and music, is broadcast over the station on 1000kc. and on short -waves 11,880kc. and 7220kc. We may be able to tune the broadcast band station at night, till closing at 1.35 am, our time, 11.05 pm Singapore and Malaya time. A five-minute news summary is presented at 13.30 am AEST. The second, or regional programme, is broadcast over on 1333kc, and short -waves 9650kc.: the night transmission concludes at 1.30 am. cur time. at ter a 30 -minute English programme from 1

o'clock. The service is operated by the British Mill-

tary Administration (Malaya), with studios In the Cathay building. Singapore.

It will be remembered by many that. In prewar days, Singapore used 1338kc, on the broadcast band, with the call -sign MIL. This station issued a very attractive verification card, showing a colorful setting sun pattern. Whether or not the service now in control at Singapore is verifying reports with this card, we.are not sure. ZHL was operated and controlled by the British Malaya Broadcasting Corporation IBMBC).

A news bulletin from Chungking is heard from a station on 640ke., which has been reported by several DX'era this month. A lady usually reads this English news bulletin at midnight. which may be heard also on abort -waves on the 30 and 31 metre bands.

In addition to the numerous short-wave frequencies used by the Armed Forces Network, Tokio, Japan. two broadcast band outlets have been heard, reported first by members of the South Australian branch of ADXRC. 590kc. and 990kc. are the channels used: the transmission usually concludes at midnight, following the normal AFRS type programmes for the Allied occupation troops in Japan. These stations usually take the same Pro- gramme, but the exact location of the transmitters is not known. It Is quite possible that one may be some distance from Tokio, providing

Japan.rlay

service for troops in another area

* * * Keeping one's list of armed Forces radio

stations up to date is certainly a problem. especially when news differs from two sources, which may be classed es official. Last issue

9AB, by the way. (Is Terry Dear, formerly chief announcer at 3AW. and remembered by many in particular for his work with Mal Vorso and Ginger. Mr. A. D. Wright also wrote us sending information about the new 9AB.

At Milne Bay, WVTC. 50 watts, 14801w.. has been handed over to the United States Navy, and verified reception recently, says Arthur Cushen, WVTC usually concludes its night transmission at 11 pm.

Another "DX'Tra" item says that the Okin- awa station WXLH. 680kc., took the air May 20 last, and is on the air most days till 10.30 pm, AEST, Mr. Geoff Woods. writing from up north advises that WXLH is using two frequencies, the second being 5025ke short- wave. Mr Woods adds that WXLD, WVTW and WVTE are among the lkw, units of APRS

Regarding WXLE, LAC A. H. Parkes says the station was, till the end of May, broadcasting from Oro Bay: it then moved for an unknown

DX reports for the January issue should be posted to reach Mr. Roy Hallett not later than Saturday, Decem- ber I, 1945. His address h 36 Baker - street, Enfield, NSW.

destination, although members of the staff believed they were bound for the Philippines. Mr. Parkes believes the frequency at Oro Bay was about 1350kc.

Mr. Suffolk reported some time back hear- ing a station he believed announced the tail sign WVTF, and the location Calcutta on 1350kc. Whether or not this has anything to do with the WVTE from Oro Bay, or the VU2ZU reported by other readers on 1365kc., we Just cannot say.

A list we were pleased to receive from Mr. Wyckhem Bailey. which our friend received from one of the AFRS stations. does not correspond entirely with other information we have. WVTE, for example. Is listed as operating on 1370kc., which may be the station we listed as an unknown AFRS station last Issue. As the list from Mr. Bailey shows station addresses, we reproduce part of It here. Reports addressed to Armed Forces Radio Station. c/o the respective APO numbers. should reach the station.

Add the station call -sign to the address, of course. -

WVTA may be addressed, AP0322. WVTO, AP0928, WVTD 11480kc.1, AP03205. WVTE I1370kc.), APO70. WVTF ,1480kc.), AP03115. WVTG, AP0920, WVTH, AF0718. WVTI. (1340kc.1, AP0718. WVTJ (1420kc,), AP0321. WVTL, AP093. WVTO 11400kc., not listed in these columns

previously 1, AP032. WVTP (1430kc.), AP0442. WVTQ (1450kc.). AP0442. (Mr. Bailey has

heard this station, suggested location may be Macassar, Mr. V, Baker has Just heard a WVTQ pn 940kc. It may be a new channel.

WVTS (1560kc.) may be station heard by Mr. Towns a few weeks ago, AP0765.

WVTT 11160kc.) not listed previously, AP031.

WVTB's frequency 1s given in the list from Mr. Bailey as 1280kc,

WVTM's power is listed as lkw. WVTR is reported to have a new APO

number. 72. by Rex Gillet. From yet another copy of "Guinea Gold."

Just to hand, again front an unknown reader, we learn that another Australian Army Amenities 10 -watt portable broadcasting station has taken the air-9AJ at Wewak. This is one of the units installed, except the aertat. in three -ton army trucks. 9AJ will operate on 1030kc., and will keep listeners posted with the latest developmenta in the Wewak area, as well as broadcast relays of sporting events, plays. news bulle- tins, Ace. troni other centres. It will be difficult, we imagine, to receive 9AJ in Aus- tralia, although some of you may manage It.

Tarawa, Gilbert Is., has been reported by Mr. Ern, Suffolk, heard around 8,80 pm on 1550ke., and Mr. Baker reports WXLB 171 10101w., in the early mornings, around 5.30 ens,

After reading our November APRS list, Mr. Don Grantley wrote us concerning some of these stations, about which he has soma information to pass on. WVTB, he says ilia gives frequency as 1, was at Nadu*.Nads, In the Markham Valley, some 40 miles from Lae, when he was there some 15 months back, and is believed to be still there.

WVTF left

c. has been at andla since beforere he l the area a year ago. WVTG has been at Blair since about two weeks after the Americans captured the place. WVTO is a mobile unit, at present somewhere in Borneo. It has been heard around Labuan.

We were surprised at the volume at which we were able to hear several "Midnight Americans." on several occasions recently. These North Americans heard during our summer months around midnight, broadcasting their early morning programmes, provide Interesting

call-signstin DX, and, as theyan- nounceifi-

cation Is not so diiult frequently, heardt

well at our location one Sunday in Novem- ber Include -KFI, Los Angeles. 640kc., mixed with a powerful Chinese station. RPO San Francisco. 680ko an NBC station, BIRO Seattle, Washington. 710kc. broadcasting CBS programmes, and others. These 60kw. stations usually verify good correct reception reports,

Station Verifications Received I By this time. many have received the mitter. 6AM, to their collection in recent

t,e.22 vnrlenatlnn 'art fl -nn, ,1+.. -. ..- __

possible with the information available. We suggest, however, that interested readers maintain their own list, based on information contained in our November issue but making changes as they become necessary. We will do our best to keep readers posted with the latest activities of these transmitters.

The call -sign of the Cebu (Philippines) transmitter listed last month as WVTR is now believed to be WVTI. Cpl. E. C. Jamieson, writing from the Polomons in August. advised us that the AFRS station at Bougainville. WVTI. had left the area, bound, he believed, for the Philippines.

WVTI has been replaced in the Solomons by the Australian Army Amenities station on 1280kc., 9AC. Mr. Jamieson says this station is operating with about 20 per cent modulation.

Another copy of "Guinea Gold" reached us recently, and again we are unable to establish the name of the person sending It along This issue contains the news that on Satur- day. September 15. the Australian Army Amenities Radio, Lae, increased power to 200 watts from 50 watts, and began using the call - sign 9AB. on 1070kc. We presume the 50 -watt unit was taken off the air when the 9AB mobile unit arrived. Officer in command at

tralian Army Amenities Service stations heard testing from Williamstown. Victoria. before leaving to join the network of 21 stations in the service up north. Some delay was necessary before the cards were issued, as printing, &c.. had to be arranged. The service appears anxious to obtain reports from listeners on any of their transmissions, which may be addressed-"Broad- cast,' 19 Heyington-place. Toorak, Victoria. Many AAS stations are now on the Job in the northern area, which may be logged by listeners on the Australian continent.

Following the special programme broadcast from 4VL Charleville, for members of the New Zealand DX Radio Club some months ago. an attractive verification card was printed. and is now being sent to those forwarding correct reception reports to the station. The card is blue and white, with designs Illustrating the Charleville district, and verification data. We also have some further details concerning the set-up at 9VL. which we shall pass on to you very soon.

Mr. Dave Harding and Mr. Bill Belford ChuDora. are among those to have added the attractive card from the Northam trans-

. /AC 44 /I ChälYl IV.11yC La rV allow ing a drawing of "The Breezy Bird" (Kooka- burra) is being issued still from this 2kw. station on 980kc. heard well in the eastern States till closing Its night transmission at 12.30 am AEST. 10.30 pm local time. Pro- grammes mainly come from studios in Perth. and are broadcast also through 6PM.

Mr. Ron Clifton and Mr. Dab Turner. Wentworthville, NSW. say 2QN is still verifying by letter, as cards are out of stock. These young newcomers are getting quite a nice collection of verts under not so favorable DX conditions.

In his letter verifying our reception of the 1kw. AFRS station WXLD Saipan. 660kc.. Sgt. Jim Moore advised listening for WXLD's sister station, WXLI. on Guam, 1380kc., which, from October 8, would also operate with an aerial power of lkw: WXLD was logged here on extended schedule during the Jap surrender period. They were logged actually around 1 am. although the signal was not very strong. Just prior to the arrival of our verification, Mr. Rex Gillett received a verification of his reception, and was informed that at that time, only one other report had been received from Aus- tralia, which was sent by Mr. Ted Tin- ning, Melbourne.

PAGE THIRTY-FOUR RADIO AND HOBBIES FOR DECEMBER, 1945

SHORT WAVES

SHORT-ViA VE NOTES BY TED %VIIITING To judge by reports to hand, excellent results are being obtained by readers on all the sh rt-wore bands. The changing conditions, making for improved night reception, arc partly responsible for this, but credit is reflected also on many readers, who appear to be at the controls just when things are

most interesting.

WE hope that the next issue will contain another long list of

new stations and verifications. Readers will notice that, this month, we

have a report from Mr. R. Simpson. who, although still to the RAAF, has a little more time to give to our hobby and is now very busily engaged in probing the ether and finding his way around again.

Of Interest to our readers is the news that the first of the line. band BBC stations used In the International Service has taken the sir, This is OSK on 20100kc, and is heard in the General Forces' service at from 9.15 pm. It is of interest that this band was opened by the BBC for its tele. vision service some fears ugo. This one is directed to South Africa at this time.

As usual, excellent signals are heard from the BBC stations. schedules of which appear in the station list.

Stations located in Central America are heard for the most part ut good level. both in the early hours and at night. but location will play a big part fit this time of the year.

From Panama. I-IP5A is heard at 7.15 am and HP50 is also heard slightly weaker at

the same time. HP5B, 0030kc, is audible again at fair level on opening at 10 pm. this station being rather spasmodic.

11113W. 10130kc, is a good one at 9.30.pm. and, in some locations. HHHM, on 96601c. I8HCM, 6185kc, and HHCW. 4000ke, are heard ut fair to good level.

Few signals are heard from the Dominican Republic, but we think that, in many cases. these stations are overlooked owing to the difficulty In identification. A few possibles are as follows: HIT 5630kc at 10.45 pm: HIlA 6190kc; HIlO 6120kc: HI1J 6026kc should be audible at about 11 pm; HIIN 6245kc at midnight: HI1X 6380kc possibly one of the signals on this band at midnight: HI1Z 6315kc, another once heard at 8.30 pm: HI3X 11850kc, reported some time ago on its changed frequency at 12.30 pm; schedule 8.10

am-12.10pm, TI4NRI1 9740kc is on a bad spot, but some may hear it at 8 am on a

gooa interference is here

9615kc bad here

sign dnlly't at 10 pm. i ELS

6165kc can be separated from FtHCM at 10.15 pm.

TGWA 151761tc is heard at 8 am: operates from I am -9.30 am. fair at times. TOWA 9780kc still heard at 4 pm closing after CBS service in Spanish. TOWS 6540kc is still on at the same time, while the new TGX1 6188ke is heard In NZ at from 1 pm till close at 2.30 pm.

A few Cubans are evident: COBC 93631tr at 9.30 pm; COBL 9835kc now again on the air at 2 put: COBQ 9220kc good some nights

B am and 10.30 pm: on 12460kc. good at 10.30 pm and 8 am; on 99581:¢. better now nt 9.30 pm; HC2AK 4655kc. heard in NZ signing at 2 pm; possibly would be heard better at 10 pm. HC2ET 47201w ut the same time,

A few suggestions for Colombia: HJAE 4965kc at 8.55 pm; HJAG 4905kc. heard locally at 7 am, weak, has changed frequency from 4975kc; HJAP 4930kc opens at 9 pm: IIJCAB 0090kc, audible weakly in NZ at 2.30 pm closing: HJCD 61801sc nt 10.30 Pro; HJCW 4945kc. fair till close at 2.30 pm Sunday; HJCX 6018kc at 10 pm: HPDE 6045kc opens at 0.30 prit, fair only.

SHORT - WAVE Reports for the January issue should be posted to

reach Mr. Ted Whiting not later than Saturday, December I, 1945. His address is 16 Louden -street, Five Dock NSW.

Notes for subsequent issues are due as follows; February, January 12; March. February 9.

Chile is In the news with the new station;; Apart from these are CE615 0130kc, heard a

9.30 pm; CE900 9600kc, on a bad spot a

2 pm; CE970 9728kc, heard closing at 2 pn in English; CE1180 11975kc, good at 9 pm on opening: CE1185 11850kc, poor at mos times.

Peru has been heard only on two frequencies, OAX4Q and OAXSC, but we think that a few of the following may be heard: OAX1A 6210kc closing at 2.30 pm; OAXIB 6565kc, poor till 1 pm: OAX4G 6140kc will be possibly heard at 11 pm; OAX5T 11800kc may be heard ut 1I pm: OAX4Z 5895kc Is on at 11 pm, used to be a fair signal; OAXID 9503kc would be Interfered with by XEWW at midnight; OAX6E 6330kc will be heard till 3 pm 111 NZ.

PRL7 9720kc, poor now at 8 am; PRLO 117201m, which has been hard to hear ut times and which gave Mr. Brunt a lot of trouble, is heard till 8.15 am; PRL9 17850ko operates from midnight till 1 am Any reports?

A very complete schedule has been received from the PMO Department, and some interesting information is Included, the full list of assigned frequencies being shown. New ones are VLC9 17800kc, VLQS 11840kc, VLR2 6150kc, VLR4 15230kc, V3.R5 21540kc, VLR6 1183Okc, VLR7 11840kc, VLR9 11850kc. VLR10 15200kc, VLW 8130kc (used some years ago), VLW4 9665ke, VLW5 9610kc !also in use some time ago!. VLA2 9520kc. VLA3 988Okr, VLA7 17800

10050kc and SUX 7865kc, both between 4 am and 5.30 am: getting noisy, though!

Tananarive, on 6140kc, Is a good one at close at 2 am, but the new one on 9700kc at 6.45 am presages more stations from that part of the world.

CR7BD 15240kc is heard at some posts till 4 pm: news in English at 3.30 pm. CR7BE 9370kc, fair some mornings, but interference at 5.30 am has been bad. CR7AA 588Okc is heard fairly well till 5.55 am, and In Queens- land, CR7B1.7 4929kc is audible at fair level with the same service.

New schedules are included In the station list for the Brazzaville network, and all frequencies are at quite good level.

Nairobi is un 6114kc at 2.15 am ut [air level. On the 4949kc frequencies, signals are heard at fair strength at times.

Algiers 12120ke heard at 4 pm In French; 11885kc at 12.15 am; 11770kc at midnight; 9610kc closes at 9 nm; 6040kc good In AFRS at 6.30 tern: CNR 8035kc Morocco closes at 6.30 ant, and this one now verifies.

From Dakar, on 11715kc, a fair signal results at 5.15 pm in Preach. and, on 88401--0, is heard well at G am: 7210kc Is the outlet used at 6 am and occasionally ut 5.15 pm.

The Eastern stations in the station list, a letter received from Mr. Hodson gives interesting detail of the Singapore transmissions. It appears that these services are In three sections, The National service is carried un 11860kc, 7220kc and 300m from 2.30 pm -4.30 pm, 8.30 pm - 1.35 ant.

The Regional service is on 9O50kc and 225m during the same hours and includes a pro -

grame tor lhe Special in that

the forces se om 7m de l available

to all Press correspondents to enable rho rapid transmission of news. For titis, all frequencies are used between 5.30 pm and 8 pm.

From 9.30 pm till 10 pm, native programmes are radiated from all transmitters; yet at 10.30 pm, both services provide different programmes in English.

* *

In the miscellaneous section, which covers Europe, are signals of great variety and interest. A few new ones are featured this month, and we hope that readers will find them good signals.

PCJ is a fine signal on 15220kc., completely swamping CHTA at times here while ore the air from 11 pin -midnight. The 9590kc. frequency is heard at 6 am -6 am. beamed to Swath Africa. One presumes that this station Is using the old antenna, which is rotated completely on a rail track. Some feat, for masts 200 feet high!

ORL3A Prague 15 weak on 11840kc. in Eng. !tall ut 6.30 ant, and calls BBC at midnight. The 9550ke. frequency is off the air at present, but, oh 60271:c.. ORL2A is heard well at 6.30 am: It is hard to separate from OWS at some poste.

From Belgrade, news Is read In French at 5 pm on 9420kc. It Is good on 61501c. at 6 am. the 6100kc. transmission being heard in a foreign service at 7 am. Best Rome station is on 6025kc., the schedule being .2.59 pm - 3.45 pm. 8.59 pm -10.15 pm. 2.29 am -7.40 am. Athol. rrnnn,nrlwc nun 19R9fLn el 191t ...n

the ibest:t COCM 9830kc good at 7 nm and 11 pm; COCO 8700kc weak at 10 pm; COCQ 88301m is still only fair at 9 pm; COCW 6344kc under bad Morse at 9.30 pm: COCX 9275kc good at 10 pm; COCY 11737kc heard till close at 3 pm; COAI 6455kc, much improved at 9.30 pm; CIK 11616kc Is heard fair at one post at 9 am. Reports, on these stations will be much appreciated as reception varies greatly with location.

South America has this month excelled Itself In- that a great variety of signals have been heard by our reporters.

ZFY, British Guiana, 6000kc, heard with BBC news at 9 pm: poor but nevertheless audible. YV1RL 4810kc, swamped by Saigon on 4800kc at 8.30 pm; YV2RC 3420kc, fine signal at 9 pm; YVSRN 4920kc, fair opening at 9 pm; Y.5RM 4890kc, one of the best at some posts at 8.30 pm. also opening: YV5RU 4860kc, weaker now at 8.55 pm: YV5KW 3400kc fades badly at 2 am: YV5RU 4790kc. heard weakly at 7 am.

Willemstad. Curacao. is one the air under call PCJ1. 17775kc, at 9 am till 10.5 am. Possibly one for the "N-Zedders."

Quito 1s heard on Its many frequencies at good level. HCQRX is u good one at 10 pm daily on 5972kc; HCJB, on 15110kc, fair at

kc. None of these stations are in use anu readers will be advised through these columns when they are put into service.

We have frequently criticised the programmes presented in our Australian Over- seas Services, and still do, but we believe in giving full credit where due. A great Job is being done to the Australian General Forces Service, which is on the air from 7.15 am till 1 ant at Intervals, these programmes being directed to the Orient for the benefit of all Allied troops.

* * Radio Somali is still heard at 1 am carry-

ing the BBC news on 7125kc. relays of the BBC and Nairobi are heard from this station.

4ccra has been heard again on 7299kc, the changed frequency being a little better at this location. Closes 4 am with "God Save the King." The 6002kc frequency has not been reported for some months.

No South Africans are heard these days. Possibly, with the change in seasons, the following assigned frequencies may be brought into use: Johannesburg 3 19046kc, 11710kc: Johannesburg 4 9902kc: Johannesburg 5 4381kc. Reports on thes: will be welcomed.

Egyptian stations are not reported this time, the best heard recently being SUV

120451:c. at 11 pm, 11810kc. at 4.30 pm, 8580kc. at 4.30 um, 6410kc, at 4.30 am.

INTERSTATE CONDITIONS

OWING to the call on space this month " by new stations and our desire to give readers as much information as possible, we have decided to omit this section, usually given in detail.

Reception over the Commonwealth has been very good, and all bands are heard at good strength. 13m. is good from 7 pm till midnight, 16m, good In forenoon, and from 7 pm till 2 ans. 19m. brings good results at nearly all times, while the bands from 25m. upwards are only good now in early morning, afternoon from 3, and at night from 5. That is briefly the picture represented by the reports received, which show much dili- gence on the part of our readers.

Reports titis month were recelvd from all States. two being received from Tasmanian readers, who have been in the Services, and who are now returning to civilian life.

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE THIRTY-FIVE

SNORT WAVES

Near Stations a od Verifications

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here le yet lee ladloree r IO re. the local ..liere In tale re eir roar sir their ore familiar hi CO." bed se Fale OM reader le.

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FAGS THIRlY.SIX RADIO AND HONKS FOR DeChlIn. 5044

SHORT WAVES

OVERSEAS S.W. STATIONS NOW AUDIBLE The following stations include those which have recently together with others which should become audible during the

of them should be audible on a sensitive ALL TIMES ARE AUSTR:. :4 EASTERN STANDA

ENGLAND GSB-9510kc. 31.55m. London. Excellent in

OF service 3.30 am -6 pm. GSC-9580kc. 31.32m. London. OF 7.15

noon. Middle East 2.30 am -4.15 am. am -6.30 am, 2.15 pm -2.30 pm.

O513-117501sc. 25.53m. London. GP service 5 pm -6 pm, 8 pm -midnight, 12.30 am -2.45 pm, fine signal.

OSE-118601tc. 25.301p. London. Good In

European service 1.15 am -7 am. 2.30 pm - 4.15 pm. 8 pm -10.45 pm.

GSF-15140kc. 19.82m. London. Poor ln GE service 2 pm -7 pm, midnight -1.45

Eastern 9 GSG-17790kc, 16.86m. London. pm -12.45 am. OF 1.15 am -5.15 am; good level.

GSH-21470kc. 13.97m. London. Fair in OF service at 12.15 am -1.45 am.

G 6260ke.

19.66m. London. pm -10.30 pm. 8.30 p dm-9 pm; African

le East

1.30 am -7 am; Pacific 4.311 pm -8 pm. Good throughout.

OSJ-21530kc. 13.93m. London. Good ln OF service from 7 pat -11.45 Dm.

GSK-26100kc. 11.49m. London. Newly Intro- duced in OF service 9.15 pm -11.45 pm.

GSL-6110kc. 49.10m. London. N. American service 12.15 pm -2.45 pm.

G Pacldc84 Rc. pm -85 pm 25.3801.

folro incn. Africa d in

4 am- 7 am: Latin 9 ant -11.30 am. only weak. 0ce 9 pm-780pm. 8 pm -midnight. 12,30 amF ó.30 um.

OSP-15310kc. 19.60m. London. GP service 4 pm -6 pm. 9.15 pm -10 pm, 7 am -7.15 am; N. American. 7.15 am -9 am: Latin, midnight -12.15 am.

OSU-7260kc. 41.32m. London. Good at close of N. American 7.15 am -2.45 Dm.

05W-17810kc. 10.84m, London. Very good In GP service 7 pm -I.15 am.

GSW-7230kc. 41,49m. London. Heard well In OF service 12.45 pm -5.45 pm.

G { GP service 8 15 pm -1.15

London. am; Latin

d one n 1.30 am -2.30 uni.

ORD-15450kc. 19.42m. London. Middle East 8.45 pin -9 pm; OF service 1.30 am -5.15 am.

G n OF

' O service 44 Opm-7 pin. 8 pm -m.

London. midnight,

ghite

12.30 am -3.45 ant; Latin, 9 am -11.30 am.

ORO-11680kc. 25.88m. London. Heard well OF 11 m-1.15 am. 3 am -51175 am:

5 PMiddl East 2.15 pm -3.30 pm. 7 P

American 7.15 am -noon. GRH-9825kc. 30.53m. London. Good at open-

ing and close of N. American service 7.15 am -2.45 pm.

ORI -94101e. 31.88m. London. DFair

only in service, Latin. 9 am -1.30 pm;

1.15 am -8.15 um. 3.30 pm -5.30 put, 8 pm- 10.45 pm.

GRJ-7320kc. 40.98m. London OF service 2 pm -3 pm, 8 am -1.30 pm.

GRK-7195kc. 41,75m. London. Used only In Latin service. 9 am -1.45 pm.

.., . ... .,...n,.,, Very good in

am- 4.45

been heard in this country, next few weeks. The majority receiver.

RD TIMl

GRY-9600kc. 31.25m. London. Heard well In all services, Latin, B am -1.30 pm, African. 3.15 stn -7 am; OF service, 2 pm -4.15 pm, midnight -1.15 am, 4 pm -5.45 pm.

GVO--18050kc. 16.59m. London. Good In Middle East. 8.30 pm -8.45 pm; GE service. 9 pm -1.15 am, 2.45 am -3.45 am.

GVQ-17730kc. 16.92m. London. This one good in OF service. 4.30 pm -7 pm. 8.15 pm - 1.15 am, 2.15 am -1.30 pm.

GVR-21675kc. 13.84m. London. , Now used in Eastern service, 9 pm -11.30 inn, good level.

GVU-11770ke. 25.48m. London. Heard In European, 2.15 am -4 ant, 8 pm -8.15 pm. 8.30 pin -10.45 pm.

GVV-11700kc. 25.64m. London. Latin service. 9 am -1.30 pm: African. 1.30 sin -7 am; GF service. 2 pin -4.15 pm.

GVX-11930kc. 25.15m. London. Heard well In OF service. 3 pm -11.45 pm, 12.45 am - 3.15 am.

GVY-11955ke. 25.09m. London, African, 4 am -7 am; European, B pm -10.30 pm; East- ern, 1 am -2 am.

GVZ-96401:c. 31.12m. London. Fine signal In Pacific. 4 pm -8 pm; N. American, 7.15 am -2.45 pat. heard at open and close.

GWC-150701m. 19.91m. London. Used to Middle East, at 7.30 pm -7.45 pm.

OWE-15435kc. 19.44m. London. Latin. 8 um -8.15 am: Eastern. 9 pat -2 am; Middle East. 2.45 am -4.15 am.

GWG-15110kc. 19.85m. London. European. 1.15 am -7 sin. 8 pm -10.45 pm; OF, 6 pm - 11.45 pm: Middle East. 2 am -4,15 am. Good most times.

OW14-11800kc. 25.42m. London. Heard in European, 1.15 am -7 alit, 4 pm -5 pm. 8 pm - 10.30 pm

GWJ-9525kc. 31.50m. London, Another In European. 1.15 am -7 am, 2.30 pm -4.45 pm. 8 pm -10.45 put.

GWL-7205kc. 41.84m, London. European, 1.15 am -7 am, 8 pm -10.45 pm; Middle East, 2.45 pm -3.30 pm.

GWN-7280kc. 41.21m. London. Latin, 9 am -1.45 pm; European, 1 am -8.30 am, 2 pm -5.15 pm. 8 pm -10.30 pm.

OWO-9625kc. 31.17m. London. Latin, 9 am - 1.30 poi; Middle East. 7 pm -7.45 pm; Euro- pean, 1 an1-8.30 am. 2 pm -5.15 pat, 8 pm - 10.30 pm.

GWR-15300kc. 19.61m. London. OF service, 3.15 pm -7 pm. 8 pm -midnight, 12.30 am - 5.15 am. 5.30 am -1.30 pm,

GWS-6025kc. 48.71m. London. European service. 2 pm -5.15 pm.

GWT-9875kc. 31.01m. London. European service. 1.15 am -7 am, 4 pm -5 pm, 8 pm - 10.30 pm.

AFN-9565kc. 35.03m. London. Good at opening at 6 pm. weakens by 8 pm; Morse bad. AFN -60801:e. 49.34m. London. Good signal In morning at 6. and till close at 5.45 pm.

NORTH AMERICA Readers requiring Information on the West

WCRC-95901:c. 31.30in. New York. Good when news read at 6 pm.

WOEA-11847kc, 36.33m. Schenectady. Good one from, 8 pm, closes 1.30 pm. Heard at intervals.

WGEO-153301tc. 19.57m. Schenectady. Closes now at 6.30 am at good level.

WGEO-9530kc. 31.48m. Schenectady. Good from 8 am; Latin service at 11.30 am: too noisy at this location.

WLWK-15250kc. 19.67m, Cincinnati. Sched- uled 8 am -10.15 ant. Heard opening,

WLWK-11710kc. 26.52m. Cincinnati. Fair nt 8 am und again at 8.45 am.

WLWK-6808kc. 49.34m. Cincinnati. Fair nt 7 am, scheduled in addition 10.30 am -3.15 pm.

WLIVLI-17955kc. 18.71m. Cincinnati. Opens at 10 pm. closes at 4.45 am. Heard with fair signal 1 am.

WLWL2-15230kc. 19.70m. Cincinnati. Good with AFRS shows at 8 amt closes at 8.45 am.

WLWL1-11810ke. 25.40m, Cincinnati. Operates -9.45 pm, 5 ant -11 um. Good signal

most times. WLWO-17899kc. 18.85m. Cincinnati. Heard

now in Latin service at 8 am. Quite good. WLWO-9590kc. 31.28m. Cincinnati. Opens

well at 6.30 am: closes finally at 3.15 pm. WLWR-15250kc. 19.0701. Cincinnati. Good

at close of transmission, 9.30 pm -7.45 am. WLWK-9750kc. 30.77m. Cincinnati. Opens

to Europe nt 8.15 am. Good level. WLWS2-183901,c. 16.31m. Cincinnati.

Scheduled 10.45 pm -12.15 am, 1.45 am - 5.30 sin, heard et 1 ant fairly well.

WLWS-15200ke, 19.12m. Cincinnati. This one in Latin service at intervals between 10.45 pm and 10.15 aus. Good at open and at 7 am.

WLWS-11710kc. 25.82m. Cincinnati. This is better signal to Latin America from 8 am till 12.30 pm.

WLWS-7832kc. 38.30m. Cincinnati. Also in Latin service 8.45 pm till 10.30 pm. WLWS-6370kc. 47.10m. Cincinnati. Good frequency check this one In Latin service nt same time. WNBI-17780kc. 16.87m. New York. Good at

7 arn, on air 11 pm -5 am. 8 am -9.15 ant. WNBI-11893kc. 25.22m. New York. Excel- lent at 6 am, operates 4.15 am -7.45 am. WNBI-11870kc. 2527nr. New York. This one heard between 9.30 am and 2 pm. WNBI-9670kc. 31.02m. New York. Heard now from 8.45 pm -10.45 pm. Not reliable. WNRA-181601:c. 16.52m. New York. Listen for this one at 1 am. heard weakly. WNRA-13050kc. 222.95m. New York. News

In French at 6.45 am. WNRA-9855kc. 30.41 in. New York.

read at 8 um, good until 9 am. WNRA-9750kc. 30 47m. New York.

opening at 9 pm. good signal. WNR&-15280kc. 19.63m. New York. Fair

at 8 am. news read at 10.30 pm. Poor at both periods.

WNRE-75651re. 39.6dm. New York Good

News

Heard

Pacific, 4 pm -6.45 pm: heard also In Latin, 9 am -11.30 am.

GRO-6180kc. 48.54m. London. Good in European service, 7.30 am -8.15 am, 3.30 pin -5.30 pm.

GRP-17870kc. 16.79m. London. Good in African service, 1.30 am -3.30 am.

GRQ-18025kc. 16.64m. London. Latin. 1.30 am 2.30 am; Middle East, 10.15 pm -10.30 pm; African, 2 ans -2.15 am. Good one, this.

GRR-6070kc. 49.42m. London. Used in GE service, 10 am -1.30 pin, not heard here.

ORS-7075kc. 42.40m. London. Heard at fair strength GF service, 2 pm -6.30 pm, 1.45 am -8.20 ana.

GRT-7150kc. 41.96m. London. European, 1.15 am -7 pm. 2.30 pm -3.45 pm, 4 pm -5 pm. 8 pm -10.30 pm: Latin, 9 am -11.30 ans,

GRU-9915kc. 30,26m. London. Good In Latin, 9 am -11.30 am, and in OF, 3.30 am -6.30 am, 6.45 am -7.45 am.

GRV-12040kc. 24.92m. London. Very good in Pacific. 4 pin -8 pm; Latin, 8 am -8.15 am fair; Middle East. 2.30 am -4.15 am, 4.45 am -5.15 ans. 5.30 am -6 am.

GRX-9690kc. 30.96111. London. Good In Pacific service, 4 pm -8 pm; Middle East. 5.30 am -8 aní.

31.mus aC feVuesteu Lo icier LIP Lise November issue. Full details will be published next month. WBOS-152101:c. 19.72m. Boston. News in French read at 9.15 pm. still good 10 pm. WBOS-9897kc. 30.31m. Boston. Operates

7.45 am -11 ant, fair early. WBOS-9570kc. 31.35m, Boston. Good one

from 3 pm. Closes 8.15 um. WCBC-94901,:c. 31.61m. New York. Scheduled

7 am -1.30 pin. Opens a few minutes earlier. WCBN-17830kc. 16.83m. New York. Scheduled

8 pm -4.45 am; no reports. WCBN-11145kc. 26.92m. New York. Good signal 7.30 ant; still fair 9 am; closes 9.15

am. WCBN-6060kc. 49.50m, New York. Operates

9.30 am -4 um; no epod Here. WCBX-17830kc, 16.83m. New York. This

outlet said to be heard 11 pm: only fair. WCBX-15270kc. 19.64m. New York. World

Elan, read at 10.15 pm. Good signal. WCBX-9590kc. 31.30m. New York. Schedule

5.30 pm -7.45 pm: fair signal at 7 pm. WCRC-11830kc. 25.36m. New York. News in

French and English read at front 8 am; fine signal.

WCRC-11826kc. 25.37m. New York. Opetis to Latin America at 9 Dm; good later.

WNRI-1307Ókc. 22.95m. New York. Opens at 8 pm and is in service till 9.15 am. WNRX-145C0kc. 20.60m. New York. Fair one In Latin service at 8 am. W000-15100kc. 19.75m. New York. Closes

now at 8.45 am, good level. WOOL-7820kc. 38.30m. New York. Fair at

5.30 pm. closes at 6.15 pin. WOOW-1I870kc. 25.27m. New York. News

read at 8.15 am, good level. WOOW-11145kc. 26.92m. New York. Weak

signal as expected at 10 am. WOOW-7820kc. 38.36m. New York, AFRS

show at 3 pin, closes at 6.15 pm. WOOW-6120kc. 49.02m. New York. Closes

at 6.15 pm. sanse service. XEBR-11826kc. 25.37m. Hermosillo. Good

one at' midnight midnight -3 am. 8 am -2 pm.

XENN-11780kc.. 25.47m. Mexico. Operates from 10.30 pin -5 pin.

XEOI-6015kc. 49.88111. Mexico. OAX4Q in- terferes at 4 pm is report from NZ.

XEOX-9 î55kc. 30.75m. Mexico. Re1a!s on B!c band till 3 pm.

XEQQ-9680kc. 30.99m. Mexico. 10 pep. 3.45 pm. Best ou Sunday from 2 pm.

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE THIRTYSEVEN

SHORT WAVES XEAQ-9815kc. 31,21m. Mexico. 11.15 am -

3.30 pm; has been heard after this time on Sunday.

XETT-9557kc. 31.39m. Mexico. On the air 24 hours daily.

XEUW-8023kc. 49.80m. Mexico. Fair signal opening at 10 pm.

XEWW-15160kc. 19.79m. Mexico. Easily followed at 11.30 pm.

XEWW-9503kc. 31.57m, Mexico. Good' till 4 pm, and very fine at 11.30 pm.

CENTRAL AMERICA AND WEST INDIES

FZF6-9715kc. 30.88m. Martinique. Was heard some time ago at 8.15 am. Any reports?

HP5A-11700kc. 25.64m, Panama. Fipe signal at 7 am. Closes 2 pm. HP5B-6030kc, 49,73m. Panama. Heard some posts at till 2 pm. Fair level at 10 pm. 1-1.1.50-117B0kc. 25.47m. Panama. Also heard at 7 am. Good signal. HP5J-9607kc. 31.23m. Panama. Heard with fair signal 8 am, and opening 11 pm Spanish and English used. HHCM-6165kc, 48,66m. Haiti. Opens at 9.35

pm. Only fair yet. HH3W-10130kc. 29.62m. Haiti. Good on opening at 9.35 pm. Verities. ' TIPG-9615kc. 31.21m. Costa Rica. Good at

10 pm. Heard in Q at till 2 pm. TILS-6185kc. 48.66m, Costa Rica, Can Just separate from HHCM at 10.15 pm. TG3-6620kc. 45.27m. Guatemala. Heard stili

till 3 pm. Weak only, TOOA-7045kc. 42.61m, Guatemala. Poor signal. Closes at 3.30 pm Sunday. TGQA-6405kc. 46.84m. Guatemala. Fair level till close at 4 pm. TGWA-15170kc. 19.78m. Guatemala. CBS service from USA at till 1 pm. TGWA-9780kc. 30.65m. Guatemala. Best from this country. Heard till 4 pm, Signs in English. TGWB-6540kc. 45.87m, Guatemala. Also heard

some posts till 4 pm, COBC-9363kc. 32,04m. Cuba, Best time is

9.30 pm. COBZ-9030kc. 33.22m. Cuba, Opens service at 9.30 pm. Usually weak. Try 1n am. COCM-9830 kc, 30.51m. Cuba. Good signal at

7 am In SA. Weak here at 10 pm. COCO-8700kc. 34.48m. Cuba. Weak at 9 pm Heard 2 pm recently. COCQ-8830kc. 33.98m. Cuba. Getting weaker at 9 pm. Fades -out later, COCW-6344kc. 47.39m. Cuba. Morse bad on this spot at 9.30 pm. Signal only weak, COHI-6455ke, 46.48m. Cuba, Noise also bad on this frequency. Can hear this one at 10 pm. COK-11616kc. 25.84m. Cuba. Any reports on this one? Operates 2 am -2 pm. COBL-9835kc. 30.50m. Cuba. Now on the air at 2 pm. Fair level. COBQ-9220kc. 32.54m. Cuba. Good some nights at 10 pm. COCX-9275kc. 32.36m. Cuba. Good signal on a good night at 10 pm. COCY-11737kc. 25.56m. Cuba. Opens at 9 pm. Heard weakly. Closes 3 pm. COK-11816kc. 25.84m, Cuba. Weak one at

9.45 am in Q. Fair at 7 am,

SOUTH AMERICA YV1RL-4810kc. 62,37m. Venezuela. Good

signal opening at 8.30 pm. YV1RV-4750kc.. 63.15m, Venezuela. Has

been heard weakly at - 9 pm. YV2RC- 3420kc. 87.68m. Venezuela. Re-

ported recently as heard well at 9 pm. YVSRN-4920kc. 60.98m. Venezuela. Opens

with fair signal 9 pm. YV5RM-4890kc. 61.42m. Venezuela. Best

from this country, opens 9.30 pm with "Woodpeckers' Song."

YV5RU-4860kc 61.73m Venezuela, 8.55 pm.

YV5RY-3380kc. 88.75m. Venezuela, heard well at times at 8.45 pm.

YV6RU-4790kc. 62,63m. Venezuela. Has been reported at one time as weak at 7 am.

PZX5-15405kc. 19.47m Suriname. Not audible now, opens at 9 pm in English and Dutch

HCRQX-5972kc. 50.23m. Quito. Still heard at times at 10 pm, fair level,

HCJB-12460kc 24.08m. Quito. Fair level 12.30 pm.

HCJB-9985kc. 30.12m. Quito, Good level after 9.30 pm.

HC2AK-4655kc. 64.44m. Quito. Heard 1n NZ signing at 2 pm.

HC2ET-4720kc 63,56m. Quito. Also heard in NZ signing at 2.30 pm.

HJCD-4840kc. 61,98m. Colombia. Good at 10 pm, chimes used before announcement.

HJCX-6018kc. 49.85m. Colombia. Fair signal at around " 10 pm.

HJDE-6054kc. 49.63m. Colombia. Opens at 9.30 pm. fair only.

CE615-6130kc. 48.78m. Chile. Very good on opening at 9.30 pm, heard consistently.

Fair at

Another

ÚE970-9728kc. 30.82m. Chile. Pair signal most posts at 2 pm.

OAX1A--6210kc, 48.30m, Peru, Heard closing at 2.30 pm.

OA3C1B-5565kc. 53.31m. Peru, Poor signal till 2 pm, heard in NZ.

OAX2A-5620kc. 53,30m. Peru, Anothei heard in NZ till 2 pm.

OAX4G--6140kc. 45.86m. Peru. Fair signal in NZ at 1.30 pm.

OAX4H-46370kc,"47.10m, peru. Also hears with fair level at 1.90 pm.

OAX4J-9340kc. 31.12m. Peru, Reported at 1 pm as fair In NZ.

OAX4N-7050kc, 42.54m, Peru. This outlet is heard In NX till 3 pm.

OAX4P-5980kc, 50.16m. Peru, Poor only in NZ at 2.30 pm.

OAX4T-11800kc. 25.42m. Peru. This one spay be heard till 2 pm in relay of OAX4Z.

OAZ4X-5895kc, 50.87m, Pero. Weak one at 11 pm locally, heard 11 am till 2 pm in NZ.

OAX6E-6330kc. 47.39m. Peru. Reported fine to 3 pm in NZ, possibly being heard at midnight.

PSH-10220kc. 29.35m. Brazil. Heard weaklly 8.30 am -9 am in Portuguese.

LRM-6130kc. 48.54m. Argentina. Weak signal from 8, pm, will improve.

LRR-11880kc. 25.25m. Argentina. Can be tuned at '1.30 am in Spanish, noise bad.

LRS1--59851tc. 50.13m, Argentina. Relays LR4 till 1 pm, fair signal In NZ.

LRY1-6090kc. 49.25m. Argentina. Opens with a fair level signal at 9 pm.

INDIA AND ASIA JLT3-15220kc. 19.71m. Tokio. 1.45 pm -5 pm,

7.30 pm -8.30 pm and from 10.30 pin. J??-11845kc. 25.33m. Tokio. Pacific Hour at

7 pm, good signal. JZJ-11800kc. 25.42m. Tokio. Weak one this

at 1.45 pm -4,45 pm. JVW3-11725kc. 25.59m. Tokio. News in Eng-

lish at 6,45 pm. Good signal. JLS-9652kc. 31.09m Tokio. Another good

outlet at 9 pm. JLP-9605kc. 31.23m. Tokio. Japanese pro-

gramme at night with English at 10.30 pm.

JZ1-9535kc. 3143m. Tokio. Used for Service Contacts at night.

JLU2-9525kc. 31.50m. Tokio, Calls KER at 9.30 pm.

Jacutta-18135kc. 16,54m. Java. Fair signal at 3.30 pm. POW at 6.30 pm at fine level.

Saigon-11775kc. 25.48m. Indo China. Good signal opens with chimes at 8 pm, POW follows,

Hongkong-11770kc, 25.49m. China. This outlet has been heard irregularly at 8 pm.

Hongkong-9505kc. 31.57m. China. This outlet on the air 8 pm -11.30 pm.

Singapore-15360kc, 19.52m. Malaya. 2.30 pm -4.30 pm, 5.30 pm -8.15 pm, Fair.

Singapore-11860kc. 25.29m. Malaya. 6.30 pm - 1.30 am. Excellent signal throughout.

Singapore-9555kc. 31.40m. Malaya. 8.30 pm - 1.30 am. Good outlet also.

Singapore-7220kc, 41.55m. Malaya. 9 pm- 1.30'am, noisy spot, but signal easily heard.

Rangoon-11860kc. 25.29m. Burma. Heard on irregular schedule 8 pm -8.30 pm.

Rangoon-6045kc. 49.63m. Burma. good signal heard in SA closing at 12.15 am. Jaffa-6790kc. 44.18m. Palestine. Close at 2 am, reopen at 2.30 am. still audible at 4 am.

Jaffa-6710kc. 44,71m, Palestine. Same schedule. Jaffa-6125ke. 48.94m. Palestine, Same schedule. Macao-7535ke, 39.83m. Port: Timor. Weak through blanket of Morse at 9 pm, carries POW news at this time. ZOJ-1527kc. 19.64m. Colombo. Good one in English at 1 pm and 2.30 pm. ZOJ-11810kc. 25.40m. Colombo. Fine signal in. English at 8.30 pm till Midnight, SEAC-11765kc. 25.50m. Colombo. This new one good at 11.30 pm. Forces programme. VUD5-17830kc. 16.83m. Delhi. 'Fine signal

all day. English at 12.30 pm. VUD8-15350í:c. 19.54m. Delhi. Fine signal

from 7 pm till after 11 pm. VUD3-15290kc. 19.62m. Delhi. Heard well

morning and night. VUD5-15190kc. 19,74m. Delhi, Very good

at all times, never seems to be off the air.

VUD-15160kc.' 19.79m. Delhi. This outlet le excellent at all tmes.

VU2ZZ-14988kc. 20.17m. India. Heard 1n SA carrying French service and using this call. Any reader supply details?

VUD9-11870kc. 25.27m. Delhi. Very good during day, heard in Japanese at 9.15 p7n.

VUD3-11830kc. 25.36m. Delhi, This station caused hetrodyne on VLW3 in afternoon.

VUD5-11760kc. 25.51m. Delhi, Fine level at 11 pm.

VUD-9690kc. 30.96m. Delhi, Very good strength at 10.30 pm in Native service.

VUD&-9670kc. 31.02m. Delhi. Very fine a0 10,30 pm in Native service In Hindustani.

VUD7-9630kc. 31.15m. Delhi. Carries Forces. service at 8' pm -11 pm.

VUD2-7290kc. 41.15m. Delhi. News in Eng- lish at 11.30 pm, good level.

X0OY-15195kc. 19.71m, Chungking, Heard irregularly at 8 am calling San Francisco.

XOOY-11915kC. 25,18m. Chungking. News in English at 9,30. am. Good signal at times.

XMHA-31860kc, 25.29m. Shanghai. " Fair with sponsored programme at 8 pm.

XGOO-11695kc. 25.65m, Shanghai, Good from 9.15 pm, carries POW at 10 pm.

XOOY-9805kc. 30.58m, Chungking. Scheduled 8.35 pm -1.30 am. Excellent level.

XGOA-9725kc. 36.86m, Chungking. Another fine signal at 10 pm.

XGOY-7155kc. 41.96m. Chungking. Apt to get a little noisy in relay of 9805kc.

XGOA--5990kc. 50.04m. Chungking. Fair through QRM at 11 pm.

XMEW---16540kc. 18.14m. China. This' one in AFRS service at from 8 pm,

Levant-8020kc. 37.41m, Berult. Heard 2.30 pm -3 pm with news in French, also heard at 3 am till 7.30 am,

AUSTRALIA AND OCEANIA

FO8AA-698kc. 42.97m. Papeete, Tahiti. Heard again at 5 am in French.

VLA-7280kc, 41,21m. Shepparton. 10.45 pm - 1 am.

VLA6-15200ke. 19.74m. Shepparton. 7.15 ant - am, Noon -3 pm, 5.30-8.15 pm.

VLC2-9680kc. 30.99m. Shepparton, 1.15am- 1.45 am, 5.30 pm -6.45 pm.

VLC4--15315kc. 19.59m, Shepparton. 8,30 am - am, 11.55 ain-12.45 pm, 1 pm -3 pm,

4.55 pin -5.25 pm. VLC5-9540kc 31.45m, Shepparton. 11 pm-

. 11.45 pm. VLC6-9615kc. 31,21m. Shepparton. Mid.- 1 am,

2 am -2,45 am, 7 pin -10.45 pm. VLC7-11840kc. 25.35m. Shepparton. 3.10 pm -

3.45 pm, 4 pm -4.40 pm. VLG-9580kc, 31.32m. Melbourne, 12,15 am -

1 am. VLG3-11710kc. 25.62m. Melbourne. 3-10 pm -

3.45 pm, 4 pm -4.40 pm, 4.55 pm -5.55 pm. VLG4-11840kc. 25.35m. Melbourne. 2 ' am -

2.45 am, 10 pm -Midnight. VLG5-11880kc. 25.25m. Melbourne. 1,15 am -

1.45 am. VL06-15230kc. 19,69m. Melbourne. Noon -

2 pm. VLG7-15160kc. 19.79m. Melbourne. Nat.

6 am -8 am daily, 6.45 am -B.15 am Sun. 9 am -10 am to Asia.

VLGlO, 11760kc. 25.51m, Melbourne. 6.10 pm - 8.50 pm,

VLQ-7240kc. 41.44m. Brisbane. Nat, 8 am - 30 am daily, 6.45 am -10.45 am Sunday.

VLQ2-7215kc. 41,58m. Brisbane. Nat, 5.30 pm - 11.30 pm daily, including Sunday.

VLQ3-9660kc, 81,06m. Brisbane. Nat. 11.45 am - 5.45 pm daily, 11 am -5.15 pm Sunday,

VLR-9580kc. 31.32m. Melbourne, Nat, 6 am - 7.10 am, 6 pm -11.30 pm.

VLR3-11880kc. 25.25m, Melbourne, Nat. 7,20 am -10 am, 11.45 am -5.45 pm daily, 6.45 am -12.45 pin, 12.50 pm -5.45 pm Sunday.

VLW3-11830kc. 25.36m. Perth. Nat. 1.30 pm - 8.15 pm daily. Noon -8.15 pm Sunday.

VLW6-9680kc, 30.99m. Perth, Nat. 8 am - 11.45 am daily, 8.45 am -11.40 am Sunday.

VLW7-9520kc. 31.51m. Perth, Nat. 8.30 pm - 1.30 am daily and Sunday.

FK8AA-6208kc. 48.39m. Noumea. Fine signal at 6 pm.

VPD2-6130kc. 48.94m. Suva. Good signal at 5 pm in religious service.

ZLT7-6715kc. 44,67m. Wellington, Good In news at 7.30 pm.

MISCELLANEOUS PCJ-152200q. 29.71m. Holland. 11 pm -mid-

night good level. PCJ-9590kc. 31.30m, Holland. Has been

heard from 5 am, hope to get schedule soon.

Tirana-6150kc, 48,78m. Albania. Reported recently at 3 am and 4 am in Italian.

ORL2A-6027kc. 49.75m. Prague. Heard now in peace at 6.30 am -7 am, calling England.

Belgrade-9420kc. 31.85m. Yugoslavia. Listen for it at 5.15 pm in English, then foreign,

Belgrade-6150kc. 48.78m. Yugoslavia, Opens at 3 am in Slav, good at 7 am. This one is erratic as regards frequency.

Luxembourg-7265kc. 41.30m, Luxembourg. Good from 2 pm, also heard at 7 am.

Luxembourg-6020kc. 49.83m. Luxembourg, News In English at 3 am.

01X3-11780kc. 25.47m. Finland. Interference, bad, but heard one afternoon at 4.30.

Warsaw-6115kc. 49.06m. Poland, "Radio Warsaw" is heard 4 am -7 am, English from 6 am -6.30 am.

PAGE THIRTY-EIGHT RADIO AND HOBBIES FOR DECEMBER, 1945

Here is a complete list of the recordings from the November - December supplement, together with first reviews of selected discs. No popular releases are given this month, but a

substantial list should be available in time for our next issue.

"SYMPHONY No. 2 IN E FLAT OP. 63" (ELGAR). The BBC SYMPHONY ORCHES-

TRA Cond. by Sir Adrian Sault. HMV ED344'49.

From the opening bars of this work, one is impressed by the flawless character of the combined efforts of all concerned in the recording; conductor. orchestra and recording staff. Ii. is one of the most outstanding pieces of recording that I have heard for a

long time: but more about this anon. The Symphony was dedicated by Elgar "Te

the memory of his la le Majesty King Edward VII . and was given a first performance by the Queen's Hall Orchestra on May 24, 1911. It Is considered to be one of the major works of English symphonic literature. and ,as such deserves a high place in the recorded reper- toire.

Some strenuous demands are made on the orchestra and the conductor, for the work calls for- the finest efforts from the players and true musicianship on the part of the conductor. With a wealth of sound detail and climax. sunerb control is necessary. As the work proceeds through tender passages to cri shing surges of .sound. Otte is intrigued tha t such can actually be recorded.

One cannot help hnl notice how the brass stands out in a most iueis(ve manner, the richness of the strings and the true tymoani- tens. Note the sweep of the haros on side 7 and the beauty of the muted strings. May wo have many more record Ines such as this It is s welcomm onnortunity to demnustrs te that the best orchestras are not all outside England.

By Audisc

LIVERPOOL PHILHARMONIC ORCHESTRA. Cared. by Constant Lambert. "CARNAVAL (ROMA) SUPPE" (Bizet t. COLUMBIA DOX746.

This is a work by Bizet that is not so well known. It is taken from a concert suite of three movements which was supposed to have been composed by Bizet whets on a visit to Rome. It. is an enjoyable tone picture of Roman carnival and contains the spirit of such a celebration.

In this work he allows his imagination full play, and the listener is transported to a Roman carnival per medium of sound ranging from quiet interludes to noisy revel- ling.

Indeed, ìt is as distinctly Roman in character as his "Carmen" is Spanish. The recording is brilliant. * *

BENNO MOISEIWITSCH .t Piano) "TOC- CATA" (Khatchtourianl and "RUSSIAN FAIRY TALE," Op 42 No. I 1Medtnert HMV Eß24.

The Toccata is an Interesting composition. fur it gets away from the style one usually- associates with Toccatas. One might call it a departure in .Tocca Las, as it appears to have been written in` what one might term "movements." . Beginning in a vague kind of way, it gradually works up to a melodic phrase which persists to the end, being developed through scherzos and adagios. The playing is excellent as is the recording.

* * * Dr. 'CHARLES. M: COURBOIN (Organ(

playing the organ of the American Academy of Arts and Letters, New York City. "BEL - 'GIAN MOTHERS' SONG" Myn Moeder- spraakt (Benoit) and "TRUMPET TUNE AND AIR" I PLrcellt. HMV ED351.

An unusual effect la the piano accom-

kaniment, presumably played on the organ

eyboard to the "Belgian Mother's Song." It is a beautiful little composition very sym- pathetically play by the great organist. The Trumpet Tune and Air is realistic; the organ used is apparently s. very versatile one, as some quaint effects and tones are recorded.

"LULLABY OF THE BELLS." Piano Con- certo from the "Phantom of the Opera" (Ward,. MANTOVANI & HIS CONCERT ORCH. Solo Pianist, GUY FLETCHER. Decca, Y5914,

A very entertaining disc combining a small orchestra of outstanding quality and a pianist of uo mean ability. The Concerto is of (he light variety taken from the well- known film and will prove a good addition to the light nuisit sect ion of the record library.

DICK LEIBEHT on the organ of the Radio City Music Hall. New York City. "COME. THOÚ MIGHTY KING" I Wesley - Gia rdinit & "THE DOXOLOGY" (Old Hundredth). HMV, EA3267.

The "Old Hundredth" is an old favorite among Xmas music. and this disc will be welcomed by all who love to sing in the spirit of the season. Both numbers are rendered with feeling by Dick Leïbert.

NELSON EDDY

RICHARD TAUBER

JUSSI BJORLING

MARJORIE LAWRENCE

HAROLD WILLIAMS

LOTTE LEHMANN

ENRICO- CARUSO

COLUMBIA . "HIS MASTER'S

RECORD REVIEW VICTOR MALE CHORUS "CONVIVIAL

MEDLEY" and "SONG OF BROWN OC- TOBER ALE," HMV. EA3269.

If you can't go to a party you can put on this record and let your imagination do the rest. The old favorites are sung in really convivial style. -The Gang's All Here," "For He's a Jolly Good Fellow," "Good Night Ladies," "Merrily We Roll Along" and "Mild Lang Syne.".

BING CROSBY (Vocal) and MAX TERRS MIXED CHORUS with JOHN SCOTT TROT- TER AND HIS ORCHESTRA. "GOD REST YE MERRY GENTLEMEN" and FAITH- OF OUR FATHERS LIVING STILL." Decca 5916.

Bing breaks away from his accustomed routine to give cs two religious numbers for the coining Xmas. I thoroughly enjoyed these two items. The mixed chorus, together with John Scott Trotter's Orch. back up Bing to make a particularly effective disc.

* FRED WARING AND HIS PENNSYL-

VANIANS GLEE CLUB WITH ORCHESTRA, Soloist, Paul Owen. "OH GATHERING CLOUDS" tBaini & "O HOLY NIGHT" (Adam ). Soloist, Jane Wilson. Decca Y5915.

More Xmas music is supplied by this combination. The two numbers are nicely rendered: the soloists in each case have pleasing voices and 'the choir is nicely balanced.

COLUMBIA JOSEPH SZIGETI IViolin), ANDOR FOLDE9

tPiauol; "Sonatina No, 1 iii D Major Op. 137, No. 1" (Schubert) (Parts 1 to 3 t, "Rondo (From Piano Sonata. In D, Op. 53)" (Schu- bert -Friedberg) LOX579'80.


Most great singers set the seal on their farne by j(p, their interpretation of an operatic role, and by the

magic of records their greatest triumphs can be

enjoyed by millions who would 'otherwise have no opportunity to

do so. Although war conditions restricted the

slmpp(Y of those records, the day will soon corne .

when they will be in

adequate supply.

SOME OF THE FAMOUS SINGERS WHOSE ART IS PRESERVED ON REÇORDS5

PAUL ROBESON

RICHARD CROOKS

FEODOR CHALIAPIN

JOHN CHARLES THOMAS

MARIAN ANDERSON

KIRSTEN FLAGSTAD

PETER DAWSON

VOICE" PARLOPHONE

The (iramuphoneCo. Ltd. (Inc, In England) Columbia Graphophone (Anat.)-Pty. Ltd, TNe`Parlophone Co. Ltd, (Inc. in England) ROM EBIISH,N.S',W. A4/45

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE _THIRTY-NINE

WORKSHOP

--WITHOUT THE BACKACHE!

30

36" I

h -9"-I PI. r

ONE TERN111AL

CENTRE OF DOARO

""O TERMINALS

FIG. F1G.3

F G

CLEAR. OP PLAYING BOARD

F4G.S

SWIVELI .66

LEAD "4

FIG.7

15RMINAL

FIG. 8

You can't always ploy skittles in the living-room, but this table-top version has the same simple fascination for guests at a small house party. Requiring only scrap materials for construction, .it can be finished off in o gqy color scheme.

By W. G. Nichols TRY

it out on the children first, if you like, but it won't be long

before father decides to "show them how."

Figure 1 gives a general idea of the whole set up. It consists of ten wooden skittles, the playing board, the skittle board which rests on, the playing board, a, wire tripod and the ball itself.

Dimensions of the playing board are shown in figure 2. Tile playing board measures 36" long and 30" wide and can be made from plywood, masonite or heavy cardboard. To three sides of this nail some 3" x 2" battens, as seen in figure 1.

Three old radio terminals are now screwed into the top edges of the two longest battens in the positions indicated. These terminals hold the metal tripod, as further illustrated in figure 8.

Next make the skittle board, the de- tailä of which are shown in figure 6. It is cut: from a piece of plywood or thick cardboard, painted black and, when dry, ten white spots, each one inch in diameter, are painted on, as. indicated.

When completed, the skittle board is placed on the playing board and three small blocks are tacked to the latter so that the skittle board can be located easily.

The wire tripod is made from three 36" lengths of stout fencing wire. Each wire must have an eye at one end, and one -inch right-angle bend at the other. A t" diameter bolt is slipped through the eyes to keep the tripod together. With a little thought, three I" diameter wooden dowels could be used to make this tripod instead of the wire.

Ten skittles are required in all. Each skittle is made from a piece of wood lf" square and 5" . long. If you are fortunate enough to have a lathe, the skittles may be turned td a round section and the general shape shown in figure 4. Alternatively, a skittle of square section may be 'made by re- producing the shape shown in figure 5 with the' aid of a fretsaw.

The ball (shown in figure 7) can be made of Aivood with a leaden insert, so that it weighs about as much as four skittles. An old billiard ball may be

he knocks down two swings it is player scores a additional swings. If he scores a "spare" he has one additional swing. One point Is scored for each skittle knocked over.

Each visit to the table is called a "frame" and ten "frames" constitute a game.

If a pin is knocked over on the forward swing, if a player fails to catch the ball at the end of the return swing, or if the ball hits the leg of the tripod, it is classed as a "gutter ball" and constitutes a scoreless "frame," in which any skittles that have been knocked over do not count.

After a little practice you can have plenty of enjoyable competition with your friends.

pressed into service. The ball is attached to a length. of cord with a small swivel, as sold by ;fishing tackle stores. The cord is then attached to the top of the metal tripod so that the suspended ball will clear the playing board by about 1 -inch.

The gaine is run as follows: The players operate in turn, a player normally .having two swings each time he visits the table. The ball must be swung in an elliptical path, hitting the skittles on the return swing. If a player

knocks down all the pins with the first swing it is called a "strike." If

all the skittles in his called a "spare." If a "strike" he has two

NOVEL FLATIRON INDUCTION heating may make its

first entiance into the household as a means of rendering obsolete the cord of the ordinary electric flatiron'. A patent issued recently to Lawrence F. Black, of the United States Army, provides for an iron, and a special base, which is çonnected to a current supply,

When the iron is set on the base it is heated by induced current set up by a primary coil in the base. The inductively energised heating element is adapted to hegt the sole plate of the iron uniformly and with maximum efficiency. An automatic pressure switch cuts off the energy when the iron is removed' from the base.

PAGE FORT' RADIO AND HOBBIES FOR DECEMBER, 1945

SAFE K$EPS FOOa COOL Christmas campers will find ía ready use for this charcoal cooling safe, made op from e kerosene tin, a box and a couple of old bags. It's more effective .thon the traditional drip -safe

and e lot more portable.

By V. K. THE writer, a Bush Missionary in

Northern NSW, has seen these "shiver boxes" in extensive use by boundary riders, railvyay workers. and others whose job carries them out into the big heat."

For the "standard" version, the materials required are one kerosene tin, one kerosene or butter box, or a few oddments of scrap timber; a couple of corn sacks and a bucketful of black charcoalcomplle'e the list.

Kerosene Tin

Wood ENSnds

Open the kerosene tin at one end and knock down the edges. . To retard rust, give it gong coat of paint inside and otetsid ,,'

Next job is to make two square wooden frames and attach one to each end of the tin as shown. The framework should protrude by about two inches; a little more is all to the good.

To protect the paint on the tin from stretching, wrap it with sacking and tack down the free end with string.

The next job is to cover the whole thing with the remaining sacking; hessian or even fire gauze will do just as well.


Turner Tack a fold of the sacking over the

goaed end of the kerosene tin and 'pack .it out with charcoal. Then bring the sacking forward towards the open end, and partly tack it to the front wooden framework.

Pack in the charcoal as you go, until the tin is completely surrounded by a layer of charcoal averaging two -

WORKSHOP inches in thickness; that is, all except the open end of the tin. Make a door for this, and attach by hinges and catch to the front wooden framework.

Instal a stout hook at each corner and add cords so that the safe can be hung in a shaded spot. A cool and draughty site is the best choice.

In use, simply tip a can of water over the whole thing every day or so, allowing it to soak into the charcoal. Then, as the water evaporates from the damp charcoal, heat is drawn from the interior-and the contents of the tin.

There are, naturally, any number of variations to the scheme and all will work, provided the main principles of insulation and evaporation' are ad- hered to.

I. R. C. ALL - METAL RHEO-

STATS are made in 25 watt and 5e_,

watt sizes. r

Though small i n

physical dimensions, the unique all -metal construc-

tion 9f d4hese Rheostats result in operating tempera-

tures being reduced to almost 'l i . half that obtained with the m i conventionèl types of rheostats.

In addition, it permits operation of the rheostat j,t All toad in any

portion of the RWepetat down to 25 per cent, of full rotation, without ex-

ceeding the normil rated temperature rise by more than 30 degrees C.

Sole Agents for Australia:

t i , I .

PAGE FORTY-ONE

BOOKS, RECORDS

TECHNICAL BOOK REVIEW Here is the latest batch of technical books to reach our office for review purposes. Supplies are available from one or other

of the booksellers advertising . in our columns. "COYNE SHOP PRINTS, MOTOS

DIAGRAMS - And How To Read Them." .Published by the Coyne Elec- trical School, Chicago. Stiff paper cover, 400 (approx.) quarto -size pages. Australian price, 16/-, plus 8d postage.

Readers who are interested in things electrical and who like poring over diagrams will certainly appreciate this book.

Intended apparently for use by Coyne students, it contains over 150 diagrams, most of them full -page size. Section one covers direct current equipment, motors, generators, meters, wiring, and winding diagrams, testing devices and a host of other detail.

Section two is similar, but deals with a -c, while the third and final section gives a small amount of radio data. Our copy from Associated Trade Journals Co., 42 Bridge -street, Sydney.

*

"THE ELEMENTARY PRINCIPLES OF WIRELESS," by W. E. Flood, M.A. Published by Longmans Green and Co., London. Paper cover, 88 pages. Aus- tralian price, 2/5, plus 3d postage.

Those who would like to obtain an elementary knowledge of radio theory. will not miss the 2/5 necessary to purchase this little book.

The first four chapters deal with wireless waves, then currents, coils, condensers and valves. Thereafter, the author explains the generation of waves, their transmission, tuning in, and the subsequent electrical processes in a receiver. The last three chapters deal with the T.R.F. and superheteroyne of reception. Considering its modest price and size, the book is well illustrated. Angus and Robertson Ltd., 89 Castle- reagh -street, Sydney.

* * * "NEWNES TELEVISION MANUAL,"

6th Edition. By F. J. Camm. Pub- lished by George Newnes Ltd. Hard cloth cover, 224 pages. Australian price, 9/6, plus 6d postage.

Dated 1945, this new edition of Newnes Television Manual is probably the most up-to-date book on the subject now available. It is not a large textbook, but the name F. J Camm is sufficient guarantee that it contains a wealth of interesting information for the average technical reader.

i

The book begins at the first principles of television, but omitting the very early mechanical systems, which are of nothing but historical interest. In 27 chapters, 'the author covers all phases of television reception and transmission-principles, practice, design, and all the rest.

In short, a book which we recom- mend for the library of every radio enthusiast.-Angus and Robertson.

* * "ELECTRONICS, TODAY AND TO-

MORROW," ' by John Mills, of Bell Telephone Laboratories. Published by D. Van Nostrund Co., New York. Hard cloth cover, 178 pages. Australian price, 15/9, plus 7d postage.

The fact that this book has already been reprinted three times since 1944

'indicates its poputarity. As suggested by the title, it does deal with modern electronic developments, but in a novel easy -to -read, "popular science" style.

The first nine chapters are concerned with what is essentially radio theory, and will, therefore, contain little that is new to the radio enthusiast. The remaining seven chapters deal with gas -filled tubes, television, electron optics, and other developments which are just now coming within the ambit of everyday technical radio.

This. is a good book for the electrician, who wishes to expand his knowledge into an unfamiliar field, without laborious study. --Angus and Robertson.

* * * "GENERAL LEATHERCRAFr," by

Raymond Cherry. Published by McNight and McNight, Illinois. Stiff paper cover, 78 quarto -size pages. Aus- tralian price, 9/-, plus 6d postage.

Here is a book which can . set you off in a fascinating and perhaps profitable hobby. Beginning with a general discussion of leathers, dyes, working tools, &c., it shows the readers sundry' tricks of cutting, sewing, embossing, lining, and other operations necessary to the making of small leather projects.

The method of making various items is described, and the final section sets out numerous decorative designs used forÜ, leather articles.--ngus and Rob- ertson Ltd.

Television in Fuir Color I

THE transmission of pictures in

full color over New York City was disclosed on Oct. 11 before the Federal Communications Commission.

Paul W. Kesten, executive vice president of the Columbia Broadcast- ing System, said that three weeks ago he saw the pictures in "magnificent color" in a laboratory over a closed circuit.

"Although nominally 525 -line pict-' ures each completed picture contained

1575 imperceptible lines of beautifully detailed color-and the circuit was complete from the scanning device to the actual receiver.

"Only yesterday, October 10, I saw these pictures successfully broadcast across the crowded New York skyline and received many blocks away with superb. clarity demonstrating the actual use of the ultra high frequencies and the modulation of a ten megacycle video band-two of the things so many were so sure could not be done."

RECORDINGS (Continued from Page 39.)

ISOBEL BAILLIE, Sop., with' Liverpool PhU- i,;;,n o).1ic 0x011., Con. -by Dr. Malcolm Sar-

eut: "The Messiah"' (Handel( Rejoice (ircatly, .0 Daughter of Zionl If God Be For Us. Who Can Be Against Us? DOX747.

ANTHONY STRANGE, Tenor: "Ave Maria" (de Georgio) (In Latin, with' Maynard Wil- kinson at Hammond organ), "Sunset" (L'Es- tremo Sole) (Aldrovancli) (In Italian, with Maynard Wilkinson at piano). 002788.

VICTOR SILVESTER's STRINGS FOR DANCING: '"Julian"-Tango (Donato), "Art- ists' Life"-Waltz (J. Strauss). 00278g.

GRENADIER GUARDS BAND: "The Big Three" -(Halter), "The Three Trumpeters" (Agostini). 002790.

GARDE REPUBLICAINE SAXOPHONE QUARTET: "Ave Verum" (Mozart, arrd. de Meyet), "Scherzo from. Quartet No. 41" (Haydn, arr. de Meyet). D02791.

ALBERT SANDLER TRIO: "On Wings of Song" (Mendelssohn), "Demande et Re- ponse" (Question and Answer) (Coleridge - Taylor). D02792.

"IIIS MASTER'S VOICE" NATIONAL SYMPHONY ORCH., Cond. by

Hans Kindler: "Festival Overture" (Wm. Schuman). RU350.

ARTHUR s'tr:11LER'S SINFONIETTA: "Christmas Symphony" (Schiassi). ED290.

UNIVERSITY OF' PENNSYLVANIA CHORAL SOCIETY, directed by Hari McDonald: "O Hone Jesu" )Palestriva), "Quacrite Primum" (Casciolini) (sung in Latin). 50295.

MARIAN ANDERSON, Cont., with William Primrose (Viola), Franz Rupp (Piano): "Vir- gin's Cran,le Song" (from "Two Songs for

ltd. Viola' -obbligato and piano") (Brahms) lin German). ED352. -

RICHARD CROOKS, Tenor, with Victor Symphony dreh., "Elijah" (Mendelssohn), "If With All Your Hearts" (recit: and aria), "'Then Shall the Righteous Shine Forth." ED353.

LILY PONS, Sop., with the Renaissance Quintet: "Air de Moulus" (Bach) (ill French), "Se to tn'ami" )Pergolesi (in Italian), EC132.

TOMMY DORSEY and ORCH., Trombone Soloist, Tommy Dorsey: "Sleepy Lagoon" (Coates), "Melody" (Dawes). EA3266,

ESTHER McNIFF CURTIS,, Symphonet: "Consolation" (song without words No. 9) (Mendelssohn), "Traumerei" (Schumann). EA3268.

BBC SINGERS, cond. by Leslie Woodgate: "Psalms We Sing" (intro. by Dr. J. W. Welch), Psalm 51: Have Mercy Upon Me, O God )Tune); Psalm 84: 0 How Amiable Are Thy Dwellings (ParràttJ: Psalm 67: God Be Merciful Unto Us (Wesley). EA3270:

CHAPEL CHOIR, with organ: "Now the Day Is Over" (Baring -Gould and Barnby), 'Holy, Holy, Holy' (Dykes). E'A3271.

ANN 'STEPHENS, vocal with Orch.: "The -Night Nursery" (Kelly-Arundale) (a) "The Sick Teddy. Bear;" (b) "Mumtnie's Song" CMcGeoch)_ EA3272.

UNCLE MAC (Derek McCuilock), talking: "Uncle Mac's Bedtime Story," "Rumpelstilt- skin" (Grimm). EA3273.

REGAL-ZONOPHONE CATFORD SALVATION ARMY SONGSTERS,

with band: "The Coventry Carol - Traditional Christmas Melody" (words "While Shepherds Watched"). "The Holy Guest" - Christmas Carol )Leldzen) (Ilford Salvation Army Song- sters), G24959.

JJICQUES HOPKINS.) the Gospel ' Singer (with organ): "Take My Life"- (Jude); "Blind Ba. rtimaens" (trad. t. G24960.

BLUE HUNGARIAN BAND: "Schubert Med- ley." introducing Moment Musical; Serenade; Marche Militaire, "On with the Waltz"- Medley, introducing Gipsy Moon; Moonlight Madonna; Kiss Me (Bitter Sweet). G24961.

HILO HAWAIIAN ORCH.: "Sailing Away from the Islands"-FT )VC), "Maori Brown Eyes"-FT (VC) (Manny Klein's Hawalians). 024962. 0

BUDDY WILLIAMS, Yodelling Jackeroo, and LENORE MILLER (with Guitar ace.): 'Bush - land Paradise," "Rhythm in the Saddle." G24962.

DECCA CHARLES LAUGHTON. reading with musi-

cal background: "Mr. Pickwick's Christmas" (Chas. Dickens). Z839/40.

CHARLES LAUGHTON, reading with musical background: "The Oldest Christmas Story" (The Gospel According to St. Luke), "The Strry of the Three Wise Men" (The Gospel Accórding to St. Matthew). Y5917.

BAND SGT. -MAJOR R. LEWIS AND ROYAL ARTILLERY SAND (Woolwich): "Concerto for Cornet" (Wright). X2192/3.

VER' LYNN, voeu with Orch Arc.: "Home, Sw't Home" (Bishop), "Love's Old Sweet Song" )Molloy). .X2194,

PAGE FORTY-TWO RADIO AND HOBBIES FOR DECEMBER, 1945

ANSWERS

UNDER THE PERSONA C.T.C. (Wollstonecratt) has installed an

Ethertone pick-up, but Is rather worried about the mounting position as no mountlnc template was supplied.

A.: This particular pick-up' does not usr an offset head so that a considerable tracking error is inevitable across the face of a 12 -Inch record. However, to judge by your diagram you have the pick-up mounted in the best average position.

R.J. B. (Alberton East, SA) is very enthusi- astic about "Monty" but wants to add an output stage

A.; Glad to note that the circuit has proved so effective and It is certainly a good idea to make the suggested addition. Your circuit is quite in order.

J.R.K. (Junabee) reporte having built up "Monty" from odd bits and pieces on hand. Reception is very good on all the short-wave bands.

A.: Thanks for your report. J.R.K., and we trust that the performance on the broadcast band will be just as good when the wire arrives for your coil.

E.R. (Coolup) is pleased to note the pros- pects of small Australian receiving valves, which will make oossible small portable and mantel receivers_

A.: Many thanks E.R., for your letter and for the renewal of your subscription, We have seen the American. midget receiver to which you refer and two or three others like it. Actually, the electrical circuit is not the problem In building sets like this, rather is It In obtaining the very tiny parts used. Although the tiny personal receivers are in- triguing, they are not in any way robust and may not have the same appeal in this country as in America

J.11í.11'. (Lonsdale Station. NSW) sends in his subscription to "Radio & Hobbies" and suggests features 'hich he would like to see.

A.: Many thanks for your letter, J.M.T., and for the subscription which has duly been recorded. We note your request for various articles, but what little space we have nowadays must be devoted to features which we consider to be of the widest general interest. We regret that we have no details of the commercial coils you mention, but you will not go very far wrong by copying the seondary turns in the way you have done. Sorry, but we are unable to supply the data for an all -wave kit. As a matter of general policy we prefer construc- tors to buy superhet coils, as improperly matched coils can cause endless bother a.nd a waste of money in the long run.

C.J.C. (Peak Hill, NSW) has built the "Radio & Hobbies' " Portable, but finds that

'It oscillates badly over most of the band. A.: We are rather surprised at you strik-

ing this trouble as the particular set should normally be quite stable. Are you sure that you have followed our layout exactly and that various plate and grid leads are not unduly long? Try connecting a 0.25 mid. condenser between the "H" plus line and earth, and try another 0.1 mfd. unit between the AVC line and earth. If you cannot locate the trouble it looks like a job for the local service man.

A.C. (RAAF, Pacific) sends in for comment a rather ambitious Signal Generator circuit.

A.: To examine your circuit to detail and comment. on all its various aspects would take up more of our time than we can spare at the moment. We have never gone into the matter thoroughly, but are not at all happy about the effect of a coil or tuned circuit across the cathode circuit of your cathode follower output. We doubt whether any ordinary coil manufaCturer would undertake to make up a kit for you, as the research necessary for the job would render the project anything but a profitable one.

M.F.F. (Erskineville, NSW) is anxious to use a 6J8 -G valve in our original "Little General" circuit.

A.: The 6J8 -G would probably operate well enough if plugged directly into the 61(8-G socket, but conditions would be far from optimum. The screens of the 6J8 -G and 608-0 should be supplied direct from B -plus through a 30,000 ohm resistor and bypassed to earth with a 0.1 mfd. condenser. . Series feed resistor to the oscillator anode will become 20,000 ohms.

L SUPERVIJION OF THE TECHNICAL EDITOR R, D. (RAAF, Q. sends In Ills subscrip-

tion to "Radio & Hobbles" and asks whether we will be sprinting any of the earlier wartime issues

A.: Many thanks for your subscription which has been attended to. There is no chance of us reprinting any of these early issues, since It would not be an economical proposition An advertisement in our "Wanted To Buy" columns should bring to light a reader willing to sell a complete set of back numbers.

QUERY SERVICES ORDINARY technical queries will be

answered on this page in strict rotation, Readers who desire answer by

mail should enclose a postal note or

stamps to the value of one shilling. We are short of staff, but will do our best

to answer as promptly as possible Make your letter clear and to the point and do not ask us to draw special cir-

cuits, as this is impossible at the

moment.

W.H.G. (Angaston, SA) has .a battery operated receiver which, apparently, be- haves in a rather erratic fashion.

A,: Without knowing the exact details of the circuit one cannot be very definite as to the cause of the various troubles. The fact that the volume Jumps up at the instant of switching off is probably to. do with the gain control circuit, the switch up- setting the bias arrangements while the filaments are momentarily still hot. This effect is fairly common and does not In- dicate any fault. If the receiver operates better without an earth connection there is no particular objection to using it that way, but make sure that your aerial is a really efficient one. The whole Idea about an aerial/earth combination is to get the best overall results, irrespective of just hold aerial or earth are installed or connected. It is strange that the set should be loud r with a higher bias voltage and it rather suggests to us that perhaps the set is intended to be used with more than 4.5 volts bias, It would be wise to check this point with the manufacturers, as the use of an Inadequate bias would make the set heavier on "B" batteries than necessary. The fact that the dial light must be on mad mean that there is a fault in the contacts of the "off -on" switch. We assume that it Is one of the three position variety in which the third position switches the dial light on as well as the filaments. Tuning on the short-wave band is usually much more critical than on the broadcast band, and your complaint in this matter may simply be due to lack of familiarity with conditions.

F.F. (Leichhardt, NSW) renews his subscription to "Radio & Hobbles" and asks about connecting a 57 valve as a triode.

A.: To connect a 57 as a triode the suppressor and screen should be tied to the plate at the socket. Alternatively, the suppressor may be connected across to cathode, but there is little to choose between the two methods. Heater, cathode and control grid perform their normal functions.

G.H. (Wollongong, NSW) had good results from "Tiny Tim II" while at Moss Vale but finds reception with the set much poorer at his present location.

A.: We are not altogether surprised at your observations since they correspond with our own general impressions of reception conditions in the two areas. There is very little latitude in a set like "Tiny Tim II" and the coil must be adjusted to meet particular conditions. Try reducing the number of turns on the primary and experimenting with the length of aerial. A wave trap in series with the lead -1n, and tuned to 2WL may help matters considerably. Your change of address has been noted,

G.A.O. (Bendigo, Vie.) asks two technical questions.

A.: Double spotting occurs normally teen

an interfering signal is on a frequency higher than the desired signal by exactly twice the Intermediate frequency. On the ' broadcast band, the resulting figure of 930kc represents a very small Increment of the signal frequency, so that the circuits ahead of the converter are less able to discriminate against the interfering signal. Mercury vapour rectifiers have a very low internal impedance while conducting, so that, under certain circumstances, extremely high peak currents may flow through them. By placing a choke immediately after a mercury vapour rectifier, the peak current which can flow is limited by the impedance of the choke. With a condenser input filter the charging current of the condenser may be high enough to endanger the. valve.

D.D. (Hill End, NSW) reports on a battery receiver which he built up using the "Radio & Hobbies' " battery amplifier.

A.: Many thanks, D.D., for your report on this receiver and we are glad to note that it has proved so satisfactory.

S.T. (Mosman, NSW) writes in appreciation of "Radio & Hobbies" and requests constructional plans for a small incubator and a ukulele.

A.: Glad to note that you like reading "Radio & Hobbies," but we are afraid that your requests are rather out of our line. If a good article on either subject comes to hand we may oblige, but certainly cannot promise anything definite.

S.J.K. (Black Rock, SA) reports having ex- perimented with several types of wind charger. Re suggests that the most efficient arrangement is to mount a propeller directly on the spindle of a North-East Model LR generator, thus eliminating need for gearing.

A.: Many thanks for your letter, B.J.K., and for the hint which has been reproduced above for the information of other readers. We note your request for a "really efficient and economical vibrator unit," but are rather at a loss to know just what you mean by this statement. The efficiency of any vibrator unit is limited to about 60 per cent. and this figure cannot be exceeded much In practice. Economy, therefore, largely depends on how much power is drawn from the unit. We will probably be describing quite a few battery sets from now on.

W.M.B. (Boonville) suggests that atmos- pheric noise could be minimised by emphasising the treble at the transmitter and - attenuating by an equal amount at the receiver. A.: The general effect you mention is well Known and is commonly employed in communication channels. However, broadcasting interests have never seen fit to adopt It as a general practice.

RADIO DEALERS We specialise in Radio Parts and stock all reliable accessories, including:

Coils - Dials - Trans- formers - Speakers - Tubular Condensers - Resistors - Electrical Accessories. Valves - Wires - Flex - Meters Multimeters - Testing Equipment. Radio Manu- als - Radio Designers'

Handbook. 1) it is available - we have it!

DAVIS RADIO CO. Wholesale Radio Distributors,

Ist Floor - Wembley House, 841 George St., Sydney.

Phone M39I7.

RADIO AND HOBBIES FOR DECEMBER, 1945 PAGE FORTY-THREE

ANSWERS

A. T. Cushen (I gill, NZ): Thanks for the letter: very helpful; will drop you a line soon. Regards.

P. W. Brunt (North Sydney, NSW): We had an idea that the station was PRLS, but thought possibly that you had hoard a new one. Thanks for the letters.

J. S. Melville (Auckland, NZ): Good log this month. Will deal with the matter you mention in the notes. S/Sgt, H. K. Clack: Your letter answered

some weeks ago. Hope things are still good up there A. W. Kew (Bankstown. NSW): Very good logs.. Will look into the new Dutch signal you heard. Pleased the set is now going well. J. Tbornthwalle (Drommoyne, NSW): Thanks for the list of "ham stations." Any reports on these are welcome. G. C. Wood (Australia): Thanks for the letter: will appreciate a report on eception from your northerly location. P. J. Byard !Launceston, Tas.): Illeased to hear from Tasmania again. Suggest you up- hold the honor of the State by submitting a monthly log. Regards.

IL Simpson (Concord, NSW): Pleated to bear from you again and hope that you will soon be turning in those new ones Good luck.

L. 11. Poynter (East Brunswick, Vie.): Very fine log again this month: the Infor- mation Is very helpful. Good luck.

O. Oaks (Stowell, Vie.): Pleased to hem that the receiver is going well. Will reply soon.

G. Obey (Bronte. NSW): Thanks for the "Ham" news. It Is most helpful.

G. D. Gilbert (Strnth(leld, NSW): The 13m band is certainly very line now, but all bands are good. Good signal from Saigon.

L. A. C. Wheeler (Perth. WA): Hope to get a regular log from you in the future Good work on the "Ham."

B. W. Battis (Corskl. NSW): Thanks inn the log. You are certainly getting arming. with the receiver.

R. Curfew (Hawthorne, Vie.): The station you mention is on commercial work. A good logging for a frequency check.

J. Hampel (Prospect, SA): As usual, reeep. Hon In your area Is very good. Thanks for the good log. Regards,

WANTED TO BUY, SELL OR EXCHANGE Readers wishing to buy, sell or exchange goods ere invited to insert an advertisement in this column. The cost is 9d per line; minimum charge 2/3. Advertisements for next issue must reach our office by Saturday, Dec. 8, 1945.

'ANTED: H type. 3 -gang Cond., £1 or offer. A. Craig, Box 20, P.O., GHgandra. \\'ANTED: Copy of "R. & H." with "'Tiny

11 Tim." Ellett. 20 Garden -st., Geelotsg. \\TASTED: "R & H," April. 1945. State price

in reply to J. E. Smith, 152 Brighton - road, (love. Adelaide, S.A.

\`'ANTED: All coptes of "R & H" from Vol. 1 No. I to Vol. 7. Price, etc.. to J. L. Lewis, 810 Ligar-street, Ballarat, Vic.

WANTED TO BUY: One 3 -gang H -tuning Condenser in good condition. R. Coates. Mingo -rood, Mingo, N.S.W.

WANTED: "R; & Il." Nov., 1943. Exchange or sell July, 1942. July, 1943, or Nov.. 1994. J. Frost, 55 Birriga-rd., Bellevue Hill. Sydney, N.S.W.

\\TASTED: All copies of "R. & H." from Vol. 1 No. 1 to Vol 4 No. 8 Inclusive. Pay 30/-. K. lanes. Box lot, Forbes, N.S.W. \,TASTED urgently by serviceman: All copies of "R. & H." from first Issue to and In- cluding .4neust. 1945. Pay reasonable price. Write NX171318 Cln. Coulson. A. J.. Florence St.. Reidlowtt, via Cnrrlmal, N.S.W.

\`!ANTED: Single gang.cond. Fur sale, complete kit, includIng cabinet D/W Little

General, used parts. What offers? Also Rola Permeg. apkr. 15.000, £ 2. Philips H & C Elim- inator, £1. Parcel assorted resistors, condensers and pots. used, £2. Used 5V40 & 6B80 valves, 10/- ea, W. J. Cade, Taylor's Arm. via Mackavflle, N.R.W.

\\/ANTED: Single gang^H cond. Fer sale. coin -

SELL: Rot. Converter, inp. 12v. out., 240 a -e .5 amp. New £9.110,-. Dy'namike, low

inn., Une trans!. telesc. stand, brand new. £7. Jewel pt. needles, play 10.000 ree £ 1115/- es, Falk, la Penkivil-st.. Bondi.

FOR SALE: All copies R.H., 6 vols.. bound. gold stamped. Best offer. J111855, Sydney.

FOR SALE: Complete set R & H first issue to date, one missing, perfect order. What

offers. Handley, Conway, Proserpine, N.Q.

FOR SALE: Applied Electricity, 8 vols.. '44 edit. Cost 117, take £12/10/-. 1.M2724,

FOR SALE: 180v. Genemotor, also headphones, etc. 9 Wallace -st., Waverley, NSW

FOR SALE: 0/100 RF MA University Meter, new. 50 Roseberry-rd., Guildford. NSW.

VOR SALE: One Phllco Output Transformer. `` Prim.. CT 10,000 Secs., 4. 8. 20. 500 ohms. 25 watts. £3. it. 3. Bell, Milne. Q.

FOR SALE: Radio Meters, 3 Weston, I

Beede. 2 Ferranti. 1 Voltmeter. radio parts, valves. Also Machinery's Handbook fenaineerlug, micrometer. slide rule. Staf- ford, "Marlow." Bundanonn, N.R.N. VCR SALE: 100 different Issues of WIDE 2- WORLD magazine in new condition. 8d each. J. Muir. 35 Merriwa-sl.. Katoomba. NSW FOR SALE: R.C.S. Dual Wave Coll Kit.

with RF stage, also RCS 4/5 coil kits. Write or call. 20 flanks -st., Ashgeld, N.S.W. 'NOR SALE: "Little Jim's Mate." new bat -

rules, valve, complete with headphones, port, case, £5. F. N. Stebbing,136 Sutherland - street. Mascot, N.S.W.

Broadcast DX W. Grayson (Newcastle): Sorry the radio has

been misbehaving. These exams and the like don't allow for much DX. All the hest,

W. Battle (Coraki. NSW): XERD W anxious to obtain reports, so they should he pleased to hear from you. Write us lust whenever You feel in the mood. we're always glad to hear from you.

A, Cushen tlnvereargill, NZ): Mane thanks for report and souvenir envelope and for the attractive New Zealand stamps.

L. Glidden (Upwry. Vie.): Sorry you found' so many difficulties running the new club. Pleased to hear some of you Intend keeping things going. Good luck.

D. Oranlley IRAAFI: Many thanks for APRS notes. We were Interested to hear about your activities as a DX'er. Pleased you decided to write us

W. Yates tBelmore, NSW): Pleased you heard the AAAS mobile test from Rose Bay golf links. Also to hear about the WLAO 7.3V curds you have.

J. Fletcher (AlF): Very pleased to hear about DX In Your area. The notes concerning your local station made interesting reading.

R. Clack IAIF): Glad to hear from yon again. Your logging SDP, ut Lubuan Is certainly good DX, 'Pleased you received their verl.

J. enrfleld (Strathalbyn. SA): Sorry you have been spending some time in bed, but you at least had the chance of doing a IIt.e more DX, No, nothing here of VL3QA, on 2840kc. calling ambulance cars.

J. Hempel (Prospect. SA): Wish I could set up all aerial system like yours in my yard. Pleased you know some of the Adelaide DX'ers,

A. Brown (Yea, Vie.): Many thanks for SIVL card and Interesting letter. Glad you find our magazine of interest, Shall write soon.

H. Mubling (helium. Old.): Pleased you heard OAC. Torakma. Our information shows frequency as 128okc., not 1257kc.. es you report, although official information is sometimes Just not quite correct,

S. Bourke (Narromine. NSW): Pleased you're only 10 off the century In veris. Also that my note Interested you. Hope 1ZM arrives soon.

Cj OR SALE: All In New Condition. Vibrator Unit. I.P. Go., O.P. I80v.. 70 M.A., £4,,10/-.

Cosmocord Xtal P.U., £2. Dynamic Mie., £2i10,'-. Aer. A: R.F. Coils with Reaction (matched). I0/- pr. 2 Single Gang Couds, 5/- ea. 8 -Inch Speaker told), 15/-. 3v.

Battery Set. £6. Or what offers? N. T. Walsh. P.O. Box 5. Mount Perry. Queensland.

FOR SALE: One six -valve amp., complete with crystal mie., crystal pick -tip arm.

turntable, 2500 ohm, 14 watt 12 -Inch Jensen concert speaker in fully -lined baffle. and 150 assorted records, hardly used. Will take reasonable otter for lot. L. Jellett, 21 Kinane St., Brighton, Vlc.

A RMATURES REWOUND. Voltages ehonged by Tradesman. All motors. generators.

Dynamotors. Late R.A.A.F. K. R. Allan, eio 4 Forsyth Street, South Belmore.

FIEYWOOD ELECTRIC SUPPLY, Heywood, Vie.

FOR SALE: S.N. VALVES, Including 1.4v, 2v, tv. BATTERY TYPES; 2.5v, Say, and miscellaneous heater type. ' Quantity S.N. CON- DENSERS. RESISTORS, and used radio parts. Also 1 -"PINES" OENESIOTOR "R" ELIMIN-

te' Mr Core Transformer, one 175kc. IF Air Core Transformer, one Slow Motion Dial (suitable for signal tracer). One RF Choke, multi -section type. Above parts must be In good order (good price given). Prices to A. D. Paull, 2 Lyon St.. Kadina, Stb. Australia.

NEW and Used Parts. 1. 2, 3, 4 Gang Con- densera, Speakers, Power Trans., Meters, Battery Chargers. Charger Rectifiers. Elimin-

ators. Scarce Valves, etc. G. Hillier. Box 13. Edgecllff, N.S.W.

ELL: 3 1K50. I 1.160, 0-1 meter, Univer- ND ally. Relnartz coll; all near new. Lot £41101-; or separate. J. O. Smith, Mosman- st.. Taringa, Brisbane.

STAMPS! The International Hobby for Pleasure and Profit, Giant Price List

Free. Cliff Howe, Atherton. South Australia

CELL: Crystal Pickups 16). brand new. lot " est type off -set head. chrome arm. perfectly balanced 11,90z nt needle point. Ar. outstanding Job. £ 12/10/- each. Hutton, 21 Drewett St., Surrey Hills, £10, Victoria.

FOR SALE: Hi -FI P.A. system with Dyn Mic. and Stand, PU and GE motor. 12in

apkr. In labyrinth. Guar. OP 15w.. £50. E. J. Goldsteen, c/o "Radio and Hobbles."

FOR SALE: Complete coils and copperplate induction gramophone motor. See "R R

H." £2151-. g3 Ramsgate -ave., Nth. Bondi, 11.1%0R SALE: Weston 0-5 AC Amp. Meter, as

new, 30/-: '. plate Cameo camera. 6 slides, case, good, £4. Or what have you for exchange? A. E. Kent, "Cranbung." Stoney Creek -rand, Beverly Hills. Sydney.

FOR SALE: University Multimeter In leather case. Model MVA (latest) ac. dc, and out-

put scales. Perfect order. Practically new. Hardly ever used. A sound bargain at £ 10. E. Aravandino, Ewing's Garage, Dalby, Qld.

[OR SALE: 2 audio transformers. coil .formers. tuning condensers. Offer. Valves

s each. UX222. PH227. A415. A445, A442. UX201A, 7/6 each or offer. One 1H00, new. 17/6. One complete 2 vntve receiver 'R & H.." Sept.. '43. model. £5/30/-. L. Fenning, Nablac, N.S.W.

HORNS (wood) FOR 12in. SPEAKER, suitable autdoor work.

JIU-JITSU. Learn 50 tricks as taught to Commandos and Guerillas; can be used effectively by Man, Woman or Child, no strength required. 2/9. KNOCK - OUT

BLOWS without fists, end amazing, -

simply applied, paralyzing, nerve pressure secrets, used by G" men. 2/9.

BE ,TALL, BE STRONG 12 hetaht-increasing and 17 etrength-building exercises. 2/9. WRESTLING. Infallible holds and throws 2/-. BOXING. The art fully explained, 2/-; or post 10/- for these live prcíusely Illuslroted courses to

L, Power, Box 3334R, G.P.O., Sydney.

PAGE FORTY-FOUR RADIO AND HOBBIES FOR DECEMBER, 1945

DECEMBER, 1945 RADIO AND HOBBIES IN AUSTRALIA PAGE III.

MORSE CODE KEY SETS AND BUZZER.

Morse Set, Highest Grade Adjust- able Morse Key. P..II.G. Typa with high Tone Buzzer. Mounted with Battery. 27/8. Adjustable Morse Set. Buzzer Battery. Fittings. Mounted ready for use. on wooden baseboard, 22/6. P.M.G. De Luse .Adjustable Morse Set on wooden base. with Buzzer. Liebt Switch. and Battery. 30/-.

instable Set. Axe

p4G l/ Morse Luxe Key, Buzz el.'Q Switch from light to buzzer. Bat- tery, mounted on baseboard. 23/.

Adjustable Morse Keys, 12/6, plus postage. Adjustable Buzzers.

1/3.

Folding Leather

Pocket and Note Waller

Combined Gold

Stamped A.I.F.. R.A.N., ur bals, bid, or t/-

11/i w

R.A.A.F. Sym- posted

POCKET KNIVES with Real Steel Blades. Hard. Long - wearing Servie ea bl e Combina t I o n Pocket or Belt Knives, for all purposes. F a r

the Man in the S the Bush- man. Sea- man. Stouts lien of the Servi r e- s,

9 Ac., d:c. Ap- f pros. 39d in. overall. s/U,

or 9/3- posted. Loop fitted for Belt. I Solid Blade. Marcia Spike'. and Tin Opener.

Also 2 -Riad,

Ill -Metal. Easy Opening Pocket Knives, Brass Handle, a life-long wearing article. 9/11. or IU/- posted. I -Bladed with Top Lifter. I./11. or 5/3 posted. AH. for hard wear. -

pgllsb-made ystal Type

GRAMO - s PHONE

PICKUP CARTRIDGES. :37/6.

Aircraft Identifica-

tion, prepared b the Publish-

ers of 'Aeroplane." 3/- ea., or I for II/-. plus postage Full of pic-

tures and fullest latest details. Part. I. British Monoplanes: 2

German Monoplanes; 4. American Monoplanes with the R.A.F.: 5,

Japanese Aeroplanes. "Kiddy Phones," A Neat Imitation Toy Telephone for the Kiddies, 6/6,

plus postage. Strongly and well made of wood.

`0frh paaETt

Refrigeration. Including Air Conditioning. and cooling and household automatic refrigeration machines. A McGraw-Hill U.S.A. oubli4ca3/Gtion.

Household Electric Refrigeration. including Gas Absorption System. A McGraw -Hilt publication. by Wostrel. 37/6, plus postage.

r. O

Mix with LUMINOUS Gun or Thin PAINT Liquid Glue. 3 posted.

NEW BOOKS FROM LONDON. How to Draw Ships. How to Draw Horses. How to Draw Children, I/9 ea., plus postage. Figure Drawing. by MaeNab. 20/-. plus postage. Air Recognition Tests. The Latest in Planes: 1/3 each. Issue of 3 In Set for 3/-. Plus onstage.

Suitchlcss Foehssing Beautiful Bakelite' 2 -Cell Torches. English make. Press bottom to light. 9/0 fitted, plus postage. Uses standard batteries.

Long -flaying Grams phone Needles. 4/11 5/3 parked and posted. 100

each plays 111 records

The Second I Overseas) Edition of

the British Radio

Amateur's Handbook.

19/fi, or I1/ -

posted and packed.

Contamina 32,1 nages of

the most valuable data on Modern Radio

Science.

The Handy- man's Mir- ror, 10/9. or

11/- posted. Gin. handle, lin. mirror. All nickelled silver. Fur a 11 Tradesmen,

Radio Builders. Watchmakers. etc See Into the cor nera and hidden

all- metalplaces.

It's andbeauti-

fully made.

Jewellers' Màgnifying Eve Glass 1ír Stamp Collectors, Mechanids.

tie. Niekelled

To Famous Books by Ghirardi. Each 22/6. plus 1/3 postage.

Radio Physles Course. En- larged Second Revised Edi- tion. A complete. Up -to - dale. Authori- tative Course.

Explains Sound Eke-

triolly. Radio. f(.p rDIO Public

Address, Pholotuóes. "ISICS 'rrlevision and

sound for the Beginner. Nearly

1100 Pages:

3,W. MOdtrD ,7.. Radio

Sen9eine. An Author*. tative One-

' Volume. Self-Study Courge 1q Practical' Re(iair "fot all kinds' of Radio.. Explains thoroughly. Radio Equgippaent, Installation. Adjustments and Maintenance: also. bow to operate a Radio Repair Service. ,110 Illustrations. Shaving: Special Safety Razor Blade Sharpener for all. 3 -Hole Blades with Free Sharpening

:tin. Highest Grade MAGNIFYING

GLASS. Nickelled Silver Rim and Handle.

Substantially made. splendidly finished. For reading or other uses. 2/in. dram.. 21/- and 2.11- Sin.. 27/6 and 301-; lin., 33/11.

NEW BOOKS just arriving from London.

Please add sufficient postage. Combat Without Arms, 2/3. The Art of Mu Jitsu, 2/6. How to Become a Commercial Artist. 2/6. British Aircraft - Part 1. Part I 9/9 each. The Modern Diesel. III/U. Model Boat Build- ing. 6/6. Everyman's Wireless Book. 8/9. Metal Work. 0/6. Practical Designs of Small Motors and Transformers, 12/6 Aircraft Radio, Spi-. A One publics ' The Design and Construction of Flying Model Aircraft, 17- One of the best published. Simple Metalwork, 11/9. Diesel Engines, 70,9. plus postage. Diesel Engineering. 24/11.

WIDEST RANGE POSSIBLE OF NEW BOOKS JUST ARRIVED

FROM LONDON. MAGIC. TRICKS, CONJURING.

ETC., ETC. Please ado sufficient postage. Lend Me Your Pack, by Forelle. 9/11. with photographs and instructions. Card Magic. by Farelle, 6/11. over 120 Items. Tom Seller's Magic Mixture, 6/11. 5h-sh-h. It's a secret by Armenian. 7/11. 2112 Methods of Forcing, by Anneman, 11/11. Super Magical IIlraeles. by Booth: all kinds of mysteries. 7/11. More card manipulations. by Jean Hueard. 7/11. Farther Studies on Mystery, by Eric C. Lewis. 3/11. Demon Magic. by Robert Harbin. S/11. Easy Card Tricks. by Levant. 2/-. Tricks Anyone Can De with Ordinary Cards -30 Rest Conjuring Tricks. by Crayford, 2/9. The Meriden Presents, by Laurie. 8/11. The Magical Compere, by Laurie. 8/11. Novel Mysteries, 7 ni each

. Pbtl 1, Original Silk Effects: Part 2, Original Card Effects: Part 3. Original Packet Effects: Part 1, Original Spiritualistic Efferte; Part 5, Miscellaneous Magic: Part 6. More Miscellane- ous Maxie. BUILD YOUR OWN MODEL

BOATS. PLANES. DOLLS' HOUSES. ETC.

Made In England. New constructional plans just'arrived from f.ondon. Easy to follow. Please add sufficient post-' age. The Belicnlas of 1020, l/R. Build the Illuminating light- ship. i'9. How to build- a' Mbdel Foci. I/9. How la Build: The Princess Doll's' House. 2/-. How to Build a £ 7/7,- Yacht from a Butter Box. 2/9 How to Build"the Sunderland Flying Boat. 2/0. How to Build a Triton Clans Sohmarine. 2/9.

Add postage. y P..ewicrnn sum,.

Metal One Cell Torch Uses stan: dard 'battery. 8/6 complete, or 5/3 posted. -

l'or Young or Old-The Musical Sensation of the Year. Easy to play, from Music Book Supplied. Anyone can play straight away. A Box of 8 colorful blocks, each with a bell note covering the full scale. Remember, no previous knowledge of music required, and you. play tunes straight away, 20/* -- blue postage. N.S.W. only. 1/6.

41,92:j --My metal finish. 11/- posted.

The CONJURER'S CASKET 01 Magic, $/G, or 4/- posted. Full Easy To Follow Directions. You can do the tricks right away.

G GOO» TRICKS-The Elusive Card Trick-The Card Monte- Che Phantom Cards-The Bal- ancing Card-The Magic Safety Pin-The Moving Peg Trick.

ratite. Safety Razor, 7/8 posted

Book of Cardl Tricks, 2/3 posted

v

Compasses I n ..,..1 4.

Metal Case. All Branches of Ser- vices, TravellersL -,42`-1

Mariners. 1Min. e

diem.. 16/6. "r ' R4, 11/3 nosted.

Stormproof-' Sure -To- - - Light, Cigarette'

Lighters. 11/6. or 12' necked and nosted

Sheffield Made Bread Knife, 2/G. or 3/- posted. Serrated Edee

No C.O.D. or V.P.P. Orders.

J. LEVE .:SON'S RADIO Games, Hobbies, . oveities and Slot Machine Specialists.

226 TT STREET. SYDNEY. Everything from A .lo .d 1tfdfoert'Sane Profit Prices. Phones M2525 and M2.í26--7. G dsForward at C.O.D. Post or Rail over 10/. (C.O.D. Rail within N.S.W. only. not Interstate).

PAGE IV. RADIO AND HOBBIES IN AUSTRALIA DECEMBER. 1945

LOOK WHAT A.R.C. HAS DONE FOR THIS MAN "!n. blessing Tite dory l started learning radio at the ,d.R.L. As things stand at present. I hate earned enough to cover

expenditures.all the Cor rse puir tor. (2) two meters l e ers value Idre -rear &'26-worth a lot more now. (3) four radios to learn on and experiment with, plus a lair amount of stock on hand. value roughly Cl5; and best of all, worth more than all. u decent /mare

Il. R. Westrro Australia

SEND FOR FREE BOOK

^'f STAFF SUPERI ,1...--.,,....,r.;.

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If so, get to work immediately and join the ambitious young men who realise that Radio offers them limit- less opportunities for advancement and an assured future.

SECURE YOUR POSITION IN THE POST-WAR WORLD

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Of fhb many Industries crying out for skilled men, none Is more important to the Nation than Radio. We offer YOU the opportunity to enter Radio NOW. Here are two good reasons why you will benefit if you become Radio -Trained: 1.-You will enter today's most progressive in-.

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PREVIOUS KNOWLEDGE UNNECESSARY

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First thing ro do If you want to secure the facts about Radio is to send it it- OSTS LITTLE

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Broadway Sydney 'Phone, M639l-2

Dear Sir.-i am interested in Please send me, without obligation part, the free book, "Careers in and Television "

on my Radio

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OF ONE MIL LIONTH OF AN INCH BY RADIO is now possible Think of it, the in- credibly small dimensions may be accurately read with electric gauges. These gauges respond to

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7 radi december, -...

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