ple mateur band aerials - world radio history
TRANSCRIPT
plemateur Band
AerialsE. M. NOLL
0)ew*olei°01oir'w1
Essex County Council
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25 SIMPLE AMATEUR BAND AERIALS
1,30001,1
saw OTHER TITLES IN PREPARATION
25 Simple Broadcast Band Aerials25 Simple Indoor and Window Aerials25 Simple MW and LW Aerials
25 SIMPLE AMATEUR BAND AERIALS
byE. M. NOLL
BERNARD BABANI (publishing) LTDTHE GRAMPIANS
SHEPHERDS BUSH ROADLONDON W6 7NF
ENGLAND
PLEASE NOTE
Although every care has been taken with the production of this bookto ensure that any projects, designs, modifications and/or programs etc.contained herein, operate in a correct and safe manner and also thatany components specified are normally available in Great Britain, thePublishers do not accept responsibility in any way for the failure,
including fault in design, of any project, design, modification orprogram to work correctly or to cause damage to any other equipmentthat it may be connected to or used in conjunction with, or in respectof any other damage or injury that may be so caused, nor do thePublishers accept responsibility in any way for the failure to obtainspecified components.
Notice is also given that if equipment that is still under warranty is
modified in any way or used or connected with home -built equipmentthen that warranty may be void.
© 1983 BERNARD BABANI (publishing) LTD
First Published - August 1983Reprinted - November 1993
British Library Cataloguing in Publication DataNoll, Edward M.
25 simple amateur band aerials. - (BP125)1 Antennas (Electronics) - Amateurs' manualsI. Title621.38'028'3 TK9956
ISBN 0 85934 100 3
Printed and bound in Great Britain by Cox & Wyman Ltd, Reading
o
4
ABOUT THE AUTHOR
Ed Noll is an established American technical author who haswritten many books, articles and instruction manuals as well ashaving lectured and taught radio communications at variousuniversities in the U.S.A.
He has worked on the staff of a number of broadcastingstations and as a consulting engineer.
CONTENTS
Page
INTRODUCTION 1
1. DIPOLE 3
2. HALF -WAVELENGTH SLOPER 5
3. INVERTED DIPOLE 5
4. TWO -MAST INVERTED DIPOLE 8
5. TWO- AND THREE -BAND INVERTED DIPOLES . . . 8
6. 3/2 WAVELENGTH AERIAL 11
7. INVERTED 3/4 WAVELENGTH AERIAL 11
8. RANDOM WIRE 14
9. DIPOLE -REFLECTOR 14
10. DIPOLE -DIRECTOR 17
11. THREE -ELEMENT BEAM 19
12. PHASED ARRAY 21
13. TWO -ELEMENT BROADSIDE 25
14. COLLINEAR 27
15. TRIANGLE 29
16. HIGH -FREQUENCY TRIANGLE 31
17. TWO -ELEMENT TRIANGLE 31
18. LITTLE VEE-BEAM 34
19. LITTLE RHOMBIC SQUARED 36
20. QUARTER -WAVE VERTICALS 36
21. TELESCOPING VERTICALS 42
22. UMBRELLA VERTICALS 42
23. PHASED VERTICALS 44
24. TWO -ELEMENT BROADSIDE 45
25. END -FIRE BROADSIDE COMBINE 50
Page
DIMENSION TABLES 53
LENGTH CONVERSION TABLE 62
EQUATIONS 63
TYPES OF CABLES 63
INTRODUCTION
Many cheap and simple aerials perform very well. Don't letthe "keep up with the Jones's aerial -farm phobia" spoil yourham radio enjoyment. You don't need the highest aerials andmaximum -gain types to have fun and relaxation. Plan, gathercomponents and erect your own. Be amazed at the fine resultsyou can obtain spending limited funds.
The twenty-five aerials, low cost and sure performers, startwith the simple dipole and proceed to beam, triangle and evena mini -rhombic made from four TV masts and about 400 feetof surplus wire.
Economy components were used in constructing all ofthese aerials over a period of many years. Aerial wire was mostoften vinyl -covered 16 SWG (14 AWG) or 18 SWG (16 AWG)solid wire that can be found in surplus outlets. Bare stranded16 SWG or 18 SWG wire was also used. A 20 -meter three -
element wire beam no more than 16 feet above ground sentout a fine QRP signal across the country.
Masts were largely the TV variety or wooden poles. Popularwas the three -section telescoping type, using the bottom twosections without guying for low aerials and one set of nylonguys when stretching up to three section heights. Bases wereset down in rocks and sand for a temporary mount, in cement,for more permanent installation. A four -section mast was usedfor some aerials, but none of the twenty-five aerials werehigher than 35 feet (WAC and DXCC were attained with under200W PEP). Shop for masts at ham and component shops orsurplus stores.
The various cables used were RG59U-58U coaxials, 450 -
ohm open wire, and good quality 300 -ohm twin lead. Coaxialline was used for the short aerials; parallel lines for the vee'sand rhombics.
A tuner is an excellent investment for the aerial experi-menter and multiband operator. Often a limited aerial -pointmismatch is not a serious loss problem. The real culprit thatsuch an aerial mismatch causes is the resultant mismatchbetween line and transmitter that can occur. Modern solid-state transmitter output drops alarmingly with mismatch. A
1
tuner avoids this difficulty. A tuner is essential when usingparallel lines. Additional benefits are the reduction inharmonic radiation and, on receive, noise level reduction andless off -channel interference. A big help is an old vacuum -valvedesign CW transmitter that can be used in tuning aerials andadjusting tuners to near final settings before connection ismade to your main transmitter.
After the aerial discussion you will find a complete set ofdimension tables that will help you to spot an aerial on aparticular frequency. Dimensions are given for various styleaerials and other data needed for spacing and cutting phasinglengths. Dimensions for the new WARC bands are also given.Now go on and enjoy yourself!
Be certain to read 1 through 7 before skipping back toother aerial types because many of the ideas introduced can beused in planning and constructing the aerial types that follow.
Ed Noll
2
1. DIPOLE
The dipole is a half wavelength aerial and is often consideredthe basic type and a reference aerial when making comparisonswith other types. It is usually centre -fed which divides it intotwo quarter -wavelength segments. End -effect makes theresonant length of a dipole physically shorter than thecalculated half -wavelength of free space. In the dimensionchart you will notice that free space half -wavelength dimen-sions are given as well as the required dipole length to obtainresonance at a given frequency. This dimension in the chartconsiders end -effect.
The dipole aerial has a figure -eight radiation pattern withmaximum direction broadside to the wire direction. The lowerthe aerial is mounted, the less directive and sharp the aerialpattern becomes.
In constructing the aerial it is advantageous to use a dipole -to -coax connector, Fig. 1. The two free ends of the dipole areconnected to end insulators. The other end of each insulator isconnect to the wire or nylon rope section that attaches to themast or other support. An attractive alternative is to use nylonrope, running it through a support ring and on down to groundlevel. Such a halyard provides a convenient means for hoistingor lowering the aerial for making changes or trim -tuning.
Theoretically the dipole should be mounted high and clearand run in a straight true line. Don't you believe it! You canhave fun and good results if it is lower, near obstacles, and iseven 30 degrees or more departed from a straight-line direction.The ultimate is great! However, sometimes you must think,"Do I need the ultimate to enjoy ham radio?"
More often than not, especially when cutting higherfrequency aerials, the aerial is not resonated at the exactfrequency you desire. Sometimes the difference is unimpor-tant. However, the influence of aerial's height and nearbyobstacles may require additional trimming. An SWR meter ishelpful in making such adjustments because the resonantfrequency of the aerial system is indicated approximately bythe frequency at which there is minimum SWR reading.
3
Hi -
--1
/4X--
0.H
1/4A
--7.
I
Insu
lato
r
Dip
ole
toco
ax c
onne
ctor
Fig.
1. D
ipol
e
Max
.
Dire
ctiv
ity
Min
.-4
1E-1
10,
2. HALF -WAVELENGTH SLOPER
The sloper is an economical dipole arrangement that savesground area and requires but a single high -support structure.The lower support can be a metal or wooden fence post. If thehigh support is a metal mast, the sloper will have some direct-ivity in the direction of the tilt as shown in Fig.2.
Another advantage is that the aerial can be tuned to adegree at the accessible low end as shown. Sections of wire canbe hung on the aerial or a jumper can be used to add a sectionof line to the aerial length when required. Thus the aerial canbe tuned for a minimum SWR at chosen segments of thefrequency band. In a typical installation, the top segmentof the dipole can be cut to the centre frequency of a givenband while the lower segment is cut to a higher frequency.Sections of line can then be jumped or added to this lowersegment to move the net resonant frequency about the bandfor lower SWR when changing operation, for example,between the CW and phone sections of a band.
3. INVERTED DIPOLE
The popular inverted dipole or inverted -V is shown in Fig.3.This is a fine performing aerial and also requires but a singlehigh -support structure. Popular opinion states that it is moreomnidirectional than the straight horizontal dipole. Also thereseems to be substantial low angle vertical radiation off theaerial ends, which favors DX operations off the two ends.Often the ends must be shortened to attain resonance on agiven frequency because of the influences of ground and apexangle.
An advantage of the inverted dipole that should not beignored is the ability to tune the aerial at the two accessibleends using hang -on sections of aerial or additional insulatorsand jumper arrangement as shown previously for the sloper inFig.2. For example, the quarter -wave segments can be cut atthe high -frequency end, say 3.8 MHz on the 80 meter band.By adding equal -length segments to the ends, such an aerial
5
Crs
Fig.
3. I
nver
ted
dipo
le
can be made to resonate at a lower frequency position on theband. On 80 metres a quarter -wave segment for operation at3.8MHz is 61.6 feet. If you wish to resonate the aerial on3.6MHz in the CW section of the band you need only addthree and a half feet to each end of the inverted dipole. If youprefer you can mount two additional fence posts to accom-modate this extra length, jumping it into operation wheneveryou desire. Many styles of aerial that have ends accessible canbe tuned in the same manner.
4. TWO -MAST INVERTED DIPOLE
A space and height saving arrangement is shown in Fig.4. Inthis dipole construction visualize the centre of each quarter -wave segment of a dipole elevated above the feed point andthe two dipole ends. Both the feedpoint and the two aerialends are at low level. However, the aerial is more compact andthe height requirements are not as great.
This aerial operated well on both 80 and 160 metres. Oneshould not expect the operation to be the same as that of adipole stretched out to full length. However, its performanceis better than most aerial types that must be compacted into asmall space. Again the aerial ends can be tuned in the mannerdescribed for the two previous types.
5. TWO- AND THREE -BAND INVERTED DIPOLES
Two or three inverted dipoles can be supported by the samemast. Matching will be excellent on each of the bands withminimum adjustment of element lengths using the samedipole -to -coax connector to a single transmission line. Goodperformance and minimum interaction is obtained bymounting the two inverted dipoles at right angles to eachother, Fig. 5 illustrates.
A three -band version may require a bit more touch-up inadjusting lengths. Maintain a 60 degree separation among thethree inverted dipoles, as shown in Fig. 5. A 20-40-80 meter
8
j1/4
X H
ooi1/
4 X
L
(a)
(b)
H =
Hig
her
freq
uenc
y of
the
two
band
sL
= L
ower
freq
uenc
y of
the
two
band
s
Fig.
5. (
a) T
wo-
band
inve
rted
, (b)
Thr
ee b
and
inve
rted
combination does very well.
6. 3/2 WAVELENGTH AERIAL
Gain in certain directions accompanied with decline in otherdirections can be obtained by increasing the length of a centre -
fed aerial to 3/2 wavelength. This divides the aerial into two 3/4wavelength segments as shown in Fig.6. Thus a reasonablematch can be obtained to a coax transmission line because theaerial resistance is low at the feed point. By orienting the aerialproperly in its mounting position the pattern can be orientedin favored directions, particularly the four major lobes. Usethe great circle path angles for your particular location toorient the aerial mounting position for performance at pre-ferred angles.
A more directional pattern with one pronounced maximumcan be obtained by tilting the legs of the 3/2 wavelengthaerials forward as shown. This construction requires threesupport locations but will give you a good maximum in somespecific chosen direction. Angle should be approximately120 degrees.
7. INVERTED 3/4 WAVELENGTH AERIAL
The 3/2 wavelength aerial can also be erected in inverted-veefashion as shown in Fig.7. Dimensions are the calculated valuefor 40 metre operation with each segment 3/4 wavelengthlong. Some end -trimming may be necessary to set a particularfrequency on the band. This aerial seems to be a good per-former with apparent low -angle directivity in the directions ofthe wire.
Consider using a tuner with this aerial permitting a lowSWR at the transmitter over the entire band. Tuner advantageswere mentioned in the introduction. An attractive advantageof tuner use for this particular aerial is its good performance asa multi -band aerial, from 10 through 80 metres. Performanceon 10, 15 and 40 metres is good, along with quite acceptable
11
Coa
x to
tran
smitt
er
43/
4 X
-11
0.-1
41-3
/4 X
Max
imum (b
)
Fig.
6.
(a)
3/4X
aer
ial (
b) 3
/4X
tilte
d fo
rwar
d
3/2
X
Lill
135°
90°
45°
',)
results on 20 and 80 metres. An aerial tuner is a necessity formulti -band operation.
8. RANDOM WIRE
Still another advantage of a tuner is its ability to providereasonable multi -band results with a random length of wire.This technique may permit you to set up a permanentinstallation of acceptable performance in a difficult location orto serve as a stop -gap or emergency aerial when required.
The length of random wire serves as both aerial and trans-mission line, connecting directly to the tuner. It is a single -wire feed arrangement. The overall length of the random wireshould be at least one -quarter wavelength at the lowestoperating frequency. This can usually be accomplished becausethe random length is composed of feed -line as well as aerial,see Fig. 8. For 80 metre operation, for example, this wouldonly be some 60 feet. A versatile tuner would permit loadingon the higher frequency bands. A disadvantage of this arrange-ment is the presence of considerable radiation near the tunerand transmitter, especially on those bands where the overalllength of the random wire reflects a very high impedance tothe tuner output.
9. DIPOLE-REFLECTOR
A parasitic aerial element has no direct connection with thedriven element or the transmission line. A parasitic reflector iscut 5% longer than the driven element and the aerial hasmaximum directivity away from the reflector as shown inFig.9. Parasitic elements can be close -spaced or wide -spacedfrom the driven element. With wide -spacing between 0.2-0.25wavelength the aerial resistance does not decrease an appre-ciable amount and a resonable match can be made to a 50 -ohmline. A tuner can be used if you wish to obtain the precisematch to the transmitter and/or take advantage of the otherbenefits of a tuner. Close -spacing values are 0.1-0.15 wave -
14
Tra
nsm
itter
1 / 4
X
Fig.
8. R
ando
m w
ire
Tun
er
(41P
-S
uppo
rt
34' 9
"
Max
imum
1/2
X d
riven
ele
men
t46
8/f
Ref
lect
or46
8/f +
5%0.
15 A
- 0.
25A
Ban
d1/
4X d
riven
234/
fR
efle
ctor
492
/fL1/
4X24
6/fs
paci
n9,..
Dire
ctor
450/
fH
10 m
eter
s8'
2"17
'3"
8'7"
15'8
"
15 m
eter
s10
'11"
23'2
"11
'6"
21'
20 m
eter
s16
'5"
34'8
"17
'3"
31'4
"
40 m
eter
s33
'4"
69'9
"34
'9"
63'9
"
80 m
eter
s65
'13
6'8"
68'4
"12
5'
Fig.
9. D
ipol
e-re
flec
tor
length. In this arrangement the two -element beam is morecompact and a bit more gain can be obtained. However, thereis a significant decrease in the aerial resistance and some formof matching arrangement is advisable. Matching stubs will becovered in connection with the discussion of the three -elementbeam.
A two -element beam for 40 metres is shown in Fig.9. Thetwo -elements are spaced a quarter wavelength. Wire aerialelements are suspended between mast pairs. Also included is atable of dimensions for the sideband portions of various bands.Dimensions for other frequencies can be determined from theextensive dimension charts at the end.
10. DIPOLE-DIRECTOR
A director is cut shorter than the driven element as shown inFig.10. Such a two -element combination shows maximumdirectivity away from the driven element toward the director.The director is cut 4% shorter than the drive element and, ifwide -spaced, there is minimum influence on the dipole aerialresistance. Thus a direct connection can be made to the trans-mission line. Again a matching arrangement is advisable whenclose -spacing is used. Typical director lengths for sidebandoperation are given.
A close -spaced two -element 15 metre beam is shown. Astub -matching plan is shown with both the stub and the trans-mission line connected to the aerial terminals. In this case theelectrical length of the aerial itself has been shortened and itdisplays a capacitive reactance at the resonant frequency. Theshorted stub provides just enough inductive reactance tocancel the capacitive reactance of the aerial. At the same timea resistive impedance match is obtained. Director spacing isonly 0.1 wavelength.
The driven element is shortened until it is just slightlylonger than the parasitic director. A coaxial T -junctionconnector is employed at the dipole aerial terminals with thetransmission line connected to one side of the T and theshortened coaxial stub to the other. Dimensions for a quarter-
17
19'
4' 8
" LC-
10' 6
" -1
10-]
10' 6
" -I
NN
-1
5' 9
"S
hort
T-ju
nctio
n or
spl
ice
To
set
Max
imum
Dire
ctor
468/
f -4%
1/2
X d
riven
ele
men
t/
468/
f0.
1 X
-0.2
5 X
Ban
d1/
4X d
riven
234/
fR
efle
ctor
492/
f L1/
4 X
spa
cing
246/
fD
irect
or45
0/f H
10 m
eter
s8'
2"17
'3"
8'7"
15'8
"15
met
ers
10'1
1"23
'2"
11'6
"21
'20
met
ers
16'5
"34
'8"
17'3
"31
'4"
40 m
eter
s33
'4"
69'9
"34
'9"
63'9
"80
met
ers
65'
136'
8"68
'4"
125'
Fig.
10.
Dip
ole-
dire
ctor
wavelength section of coaxial line with a velocity factor of0.66 is given in the dimension charts. A quarter -wavelengthsection was first used and shorted at the end and thenconnected to the T junction. Most likely the SWR reading willbe high. Now cut off tiny sections of the shorted end of thestub and re-establish the short each time. Do so until aminimum SWR is obtained. In the sample the ideal matchcame when the stub length was 5'9". A standing wave ratioon the line was 1.05 at 21.3 MHz. Band -end SWR readingswere less than 1.15.
11. THREE-ELEMENT BEAM
The three -element beam provides additional gain and direct-ivity. Close -spaced wire beams require less mounting area and,as shown in Fig.l 1, only four support masts are required.Plastic lines are suspended between the masts to support thedriven element.
The two beams shown are dimensioned for operation on 40and 20 metres. Reflectors are 0.15 wavelength from the drivenelement; directors, 0.1 wavelength. You will surprised at theresults with the beams no more than 16 feet above ground.
Aerial resistance is low and some form of matching isrequired. Stub matching is suitable and effective when usinglow -loss parallel lines (450 -ohm open line or good quality 300 -ohm ribbon line) to connect the beam to the transmittertuner. The basic stub arrangements are shown in Fig.11. In thefirst quarter -wavelength section of transmission line beginningat the aerial terminals, the impedance rises from minimum tomaximum. Somewhere along this span there is a point of thesame impedance as the transmission line. The lower the aerialresistance or the higher the transmission -line impedance, thegreater will be the separation between the aerial terminal andthe point at which the transmission line is attached for bestmatching. Try various positions for the transmission lineattachment until you locate the point of minimum SWR usingyour aerial tuner and SWR meter.
The second stub indicates an arrangement that can be used
19
Pla
stic
line
Fig.
11.
Thr
ee e
lem
ent20
'11"
13'1
1"
1
Mor
e1/
4or
less
than
Ban
d1/
4 X
driv
enel
emen
tR
efle
ctor
Dire
ctor
Spa
cing
0.1
0.15
0.2
0.25
234/
f49
2/f L
450/
f H
108'
2"17
'6"
15'3
"3'
5"5'
2"6'
10"
8'6"
1511
'23
'5"
20'1
1"4'
8"6'
11"
9'3"
11'6
"20
16'6
"35
'1"
31'4
"6'
11"
10'5
"13
'9"
17'4
"40
33'4
"69
'9"
63'9
"13
'11"
20'1
1"27
'11"
34'9
"
if the aerial also displays a reactive component. A somewhatlower SWR can be squeaked out by making the stub more orless than a quarter wavelength. However, in a practical situa-tion with a quality tuner this step is seldom necessary. If youwish to use the coaxial line the special arrangement of Fig.10using a foreshortened driven element is convenient and reallybrings down the SWR on the line.
Matching adjustments with modern solid-state transmitterscan be touchy because you must be careful when a high SWRcomes on the line in the tuning process. Thus adjustmentsinitially should be made at as low a power level as possible.If you have a particular interest in aerial experimentation,keep an old low -power vacuum -valve transmitter handy. Allearly trimming and tuning adjustment to the aerial system canbe made before the aerial is connected to your main trans-mitter. Now only touch-up adjustments are needed.
12. PHASED ARRAY
A variety of horizontal phased arrays can be constructed atlow cost using wire aerial elements and supports. Two -elementend -fire, broadside and collinear styles provide gain anddirectivity as compared to a single dipole.
The end -fire configuration can be spaced for either bi-directional or uni-directional operation as shown in Fig.12.Two half -wavelength dipoles separated by half wavelength anddriven out -of -phase, provide a bi-directional good figure -eightpattern obtaining maximum radiation broadside to the aerialwire if properly fed and tuned. Resultant gain can approachapproximately 4dB.
A fine unidirectional cardidoid pattern is obtained by usingquarter -wave spacing and quarter -wave feed. As shown inFig.12, a quarter -wave section of line is located between dipoleto which the transmission line is attached and second dipole.Maximum gain is in the direction of dipole that is fed a lagging90 degrees, shown by the arrow in Fig.12.
The remainder of Fig.12 shows various feed arrangements.In the first set of three, there are three 180 degree end -fire
21
16'6
"
Fig.
12(
b).
16'6
"
16'6
"0
16'6
"
arrangements. The elongated figure -eight pattern is obtained byfeeding one dipole and then the second one 180 degrees laterwith a half -wave section of line. The same results can beobtained by centre -feeding and then transposing one of thequarter -wave segments as shown.
The third drawing shows the coaxial feed technique. Notethat the center conductor of one feed section goes to the leftsegment of one dipole while the centre conductor of the othergoes to the right segment of the second dipole. As a result thetwo dipoles are fed out -of -phase.
The four remaining drawings demonstrate unidirectional90 degree feed. Note in the simple parallel feed arrangementthat the unidirectional pattern can be shifted by simply trans-posing the 90 degree feed line that connects between the twodipoles. Unidirectional pattern is always in the direction of thedipole that is fed 90 degrees lagging. When erecting such anaerial you might plan to make it convenient to make such atransposition. It need not be done at the centre as shown butcan be accomplished at one of the two dipole feed points.
You can do the same thing using T -junction coaxial feed. Inof coax
from one side of the T -junction to one of the dipoles and aquarter -wave section of feed line to the second. Directivity isdetermined by proper connection of the inner conductor andshield of the coax segments of the two dipole elements, asshown. Pattern reversal can be obtained simply by transposingeither one of the feed lines at the point where it connects toits associated dipole.
13. TWO -ELEMENT BROADSIDE
In a horizontal broadside arrangement the two dipoles areplaced one above the other for a two -element combination asshown in Fig.13. Horizontal radiation patter is a figure -eightwith maxima broadside to the plane of the two dipoleelements. Both the horizontal and vertical radiation patterns areshown in Fig.13. The vertical radiation pattern is also a figure -eight and, therefore, does some concentrating of the vertical
25
Hor
izon
tal
Ver
tical
Fig.
13.
Bro
adsi
de
5/8
X
radiation at the favored low angles.Dipoles must be fed in phase as shown. In the first feed
method there is a half -wave section of line between thebottom and top dipoles. Ordinarily this would produce an out-
of -phase feed. However, the line is transposed and, therefore,the two dipoles are fed in -phase. Another way of obtaining in -
phase feed is to use a centre feed point. Two dipoles can beseparated a half wavelength and fed in -phase with this method.Furthermore any separation between the dipoles can be usedand in -phase feed will result. If space is available you may wishto try a 5/8 wavelength separation which will result in afurther lowering of the vertical radiation angle.
14. COLLINEAR
The horizontal collinear is not used too frequently because ofspace requirements. However, you may wish to experimentwith this phase combination on 10 or 15 metres. In thecollinear arrangement, Fig.14, two dipole elements are placedend -to -end. However, for good performance it is necessary thatthe two ends be well separated. The collinear pattern is asharpened figure -eight that is broadside to the collinearelements.
Two basic feed arrangements are shown. In the first one thetwo half -wave elements can be brought near to each otherbecause a high impedance feed is used. Note that the parallelline connects to the two ends of the separate half -wavelengthsegments. The open -wire line should have an overall lengththat is an odd -multiple of a quarter -wavelength so as to presenta low impedance at the point where it connects to the tuner.
The second feed arrangement is a coaxial line, low -impedance one. Both collinear elements are centre -fed andtheir respective feed lines are connected to the main coaxialtransmission line back to the transmitter by way of a T -junction.
27
N 00
15. TRIANGLE
The triangle is another low-cost aerial that performs extremelywell. It is a full -wavelength aerial, like the quad and delta loop,without being so clumsy and subject to weather damage. It issimple, strong and easy to erect as shown in Fig.15. On 40, 80and 160 metres, where the other full -wavelength aerials arejust about impossible, the triangle is an easy assembly.
The very centre of the full -wavelength wire is attached atthe top of the support mast with an insulator. The two legsfan out and fold back on themselves. The ends are returned tothe mast to a dipole connector or other form of insulator. Thetriangle can then be stretched out on each side using nylonrope and two metal fence posts. You will find it is a very rigidassembly, acting also as partial guying for the mast. It is notnecessary that the triangle be equal -sided (equilateral). In somemounting situations it may be advantageous to have thetriangle base a different length to the other two sides. Theimportant thing is to have the loop resonate as a full wave-length loop.
The base of the triangle need only be 7 to 8 feet aboveground to avoid traffic. Aerial impedance is low because thebase of the triangle is so near ground. As a result you can makea direct match to coaxial line. The feedpoint at the very centreof the base is accessible using a short stepladder.
A starting point for calculating the length of the trianglewire is the equation for a full wavelength in space (WireLength = 984 fmHz). The proximity of ground may requirethat the triangle be shortened somewhat below this calculatedvalue after it is erected. It is easy to do so because of the lowheight of the wire ends.
When the base of the aerial is raised as it most likely wouldbe for 10, 15, 20 and even 40 metres, the resonant -wire lengthmay even be greater than the full -wavelength free -space calcu-lation. The aerial resistance increases as the triangle is elevatedhigher above ground and some form of matching may beneeded. If you use open -wire line and a tuner this need not bea consideration.
The triangle shows directivity that is broadside to the plane
29
Insu
lato
r
Met
al fe
nce
post
Pla
stic
clot
hesl
ine
( X
)dr
iven
tria
ngle
Fig.
15.
Tri
angl
e
of the triangle. However, omnidirectional performance is quitegood but you may wish to orient it in its mounting positionfor some favored direction. Orientation can be changed veryeasily from ground level.
16. HIGH -FREQUENCY TRIANGLE
A high -frequency triangle can be constructed in the two basicways shown in Fig.16. A wire triangle can be constructedsimilar to the low -band version. Insulators and nylon rope areattached to the base angles. It can be pulled out and supportedfrom ground level. The wind will not blow this loop down.
An alternative approach is to use self-supporting tubing forthe base of the triangle. A thick plastic sheet can be used tosupport the base elements to the mast. The ends of the tubingcan then be linked to the apex of the triangle with wire oradditional tubing. Dimensions are given for 20 -metre opera-tion. Total length of wire is 69 feet. Stub matching to coax orparallel line can be used. Using parallel line an aerial tuner isall that is necessary. You will be surprised at the performanceof this single -element aerial that can be built at such little cost.
17. TWO -ELEMENT TRIANGLE
Reflector and/or director triangles can be added to increasethe gain and sensitivity of a triangular configuration in a pre-ferred direction. Spacing between driven triangle and parasiticneed only be 0.125 wavelength, Fig.17. This is an 8th wave-length and can be determined by halving the dimension shownunder the quarter -wavelength free -space values given in thedimension charts. In general, wire length should be 5% longerfor the reflector and 4% shorter for the director. The drivenelement itself in close proximity to the parasitic element mayrequire additional length. Often the driven element isdimensioned 1000/f instead of the basic 984/f. Reflectorwould be 5% longer and director 4% shorter than this newvalue.
31
Alu
min
ium
tubi
ngP
last
ic s
heet
0.12
5XA
10(
Par
asiti
c xitic
Ref
+ 5
%D
irect
or X
-5%
(X)
driv
en
Fig.
17.
Tw
o-el
emen
t tri
angl
e
Ref
lect
or s
tub
In so far as 40, 80 and 160 metre operation is concerned a
single additional support mast is required to support the two -
element beam. This is indeed a low-cost beam compared to
any type of beam that is to be constructed for these bands.
Furthermore it is of sound physical structure and not weather -
prone.In high -frequency operation it could be supported strongly
by two cross members joining the apex of driven element to
apex of parasitic, along with another cross beam between the
centres of the two bases.The lowness of the 40, 80 and 160 metre triangles means
the base of the parasitic is accessible. Thus it could be dimen-
sioned to operate as a director. However, an additional stub
could be added as shown in Fig.17 along with a sliding short.
With the short positioned at the insulator the parasitic will
operate as a director. By sliding it down the stub the proper
length, the same element could be operated as a reasonable
reflector as well.Additional triangles may be mounted within the triangle
of the lowest frequency operation. This is similar to the
arrangement employed in multiband quads. A 40 and 80 metre
combination is an attractive arrangement. Parasitics could be
added in the same manner.
18. LITTLE VEE-BEAM
Did you ever wish to experiment with a vee-beam or arhombic? You thought it was too expensive and you lack the
space. Not so. You can put up a short vee-beam or rhombic.
Although performance will not duplicate the performance of a
very long one, the performance of these short beams will
surprise you. A practical, good performing vee-beam is shown
in Fig.18. Leg lengths can be 95-100 feet which corresponds
to approximately 3/4 quarter -wavelength on 40 metres. It does
fine on 40 metres. Higher-frequency bands have leg wave-
lengths which exceed 3/4 quarter -wavelength and gain and
directivity rise. If you want to send out a good QRP signal in
some favored direction on all of these bands the lil'vee-beam
34
deserves a try. Use open -wire line or good -quality 300 -ohmline and a tuner. The aerial will also load up on 80 metres andgive reasonable results. An apex angle between 65-75 degreesis acceptable.
19. LITTLE RHOMBIC SQUARED
The small rhombic of Fig.19 was our good performer for anumber of years. You need a mounting space about 100 footsquare. The four sides are of the same length and all angles are90 degrees. It is a perfect square. The rhombic was supportedby four 3 -section TV masts, each guyed with nylon rope.Open -wire line and a tuner were used.
The aerial is fed at one corner while the opposite corner isleft open. This manner of operation establishes a bi-directionalpattern. An acceptable uni-directional pattern is obtained byterminating the far corner in a 450 -ohm non -inductive resistor.
If you wish to change the aerial pattern on occasion youmay do so by moving the wire jumpers that connect the trans-mission line to any one of the three remaining corners. Youmust remember to move the two jumper wires to the othertwo corners when you do so. Halyard arrangements for thevarious corners are helpful if it is your intent to changedirectivity.
Excellent performance with this small rhombic wasobtained on 10, 15, and 40 metres. Acceptable results wereobtained on 20 and it would also load for QSO's on 80 metres.
If you wish to operate the aerial in an omni-directionalfashion you can do so by connecting jumpers at all fourcorners. Feed the aerial at the centre of one of the sides.
20. QUARTER-WAVE VERTICALS
The fundamental vertical aerial is a quarter -wavelengthradiator, Fig.20. This is not a true vertical dipole because thephysical length of the aerial approximates just one-half thelength of a dipole. However, the ground acts as a mirror
36
rig.
19.
Litt
le r
hom
bic
squa
red
1/4
Xve
rtic
al
Bol
ts
Gro
und
supp
ort
mas
t
Fig.
20(
a)/A
IX v
ertic
als
Pla
stic
tube
l 4.1
VD
1 / 4
X
Woo
d2"
x 3
"
U-b
olt
L., 4
.:D
ipol
eW
ood
1" x
2"
conn
ecto
ror
Rad
ials
2" x
3"
Met
alfe
nce
post
Fig.
20(
6)
Gro
und
leve
l
quarter -wavelength segment. Ground conditions, in fact, have
an influence on performance of the vertical aerial. The mirror
segment of the vertical can be ground itself, or it may be anetwork of wires or tubing that acts as an artificial ground. If
placed on the surface of the ground or a few inches belowground, such a low -resistance conducting surface can result in
a substantial improvement in aerial performance and uniformity
of matching. Often a metallic ground (called a ground plane) is
also employed when the quarter wavelength radiator is
elevated above this physical ground. In effect, the groundplane brings the ground up to the level of the aerial.
An advantage of a vertical aerial is its omni-directionalhorizontal pattern. It is circular and indicates the radiation ofequal level signals in all compass directions. Groups of vertical
aerials can be used to obtain a direction pattern when desired.
The vertical radiation pattern approximates a half figure -eight.
This type of pattern concentrates the radiation at low vertical
angles. Little energy is radiated skyward while the favorable
low -angle radiation is obtained.Very low-cost verticals can be constructed for 10 and 15
metres using strong pieces of plastic as shown in Fig.20. The
same applies to the 20 -metre vertical except that sturdier
components are required. In the case of a 40 -meter vertical awooden support system must be constructed to add additional
support for the structure.The first two examples of Fig.20 show how plastic rods and
plastic tubes of adequate wall thickness can support a shortvertical. The ground rod can be made of the same material as
the radiator itself. Holes are drilled through the radiator tubing
and the plastic rod. Inserted bolts make the connections to
both the radiator and the ground rod. A dipole -to -coax
connector can be jumped between the two sections to permitconnection of the transmission line.
When you can obtain a thick-wall plastic tube the radiatorand ground rod can be inserted into the tube as shown in the
second example. These two simple arrangements will easily
support 10 and 15 metre ground -mounted verticals.The third arrangement shows how a long plastic rod can
support a light -weight vertical. The vertical fits over the rod
40
and the inner conductor of the coax line connects to one ofthe holding bolts. A separate ground rod is then connected tothe shield of the coax line. No coax connector is needed withthis arrangement.
The fourth arrangement shows how a whip vertical canbe supported on insulators that are mounted on a wooden1" x 2" or 2" x 3" batten. Inner conductor connects to thewhip and the shield to the ground rod. Ground rod should be6 to 8 feet long. An alternative is to have a shorter ground rodand then solder or bolt at least four radials to the rod, placingthem about one or two inches beneath the ground, stretchingthem out and separating them by approximately 90 degrees.Resonant -length 1/4X radials help in matching and holding upaerial resistance.
The fifth scheme shows our favorite mounting arrangementIn this arrangement the radiator is U -bolted to a wooden2" x 3" or 2" x 4" batten. The wooden support is 8 foot longand mounted 3 foot into the ground. A short ground rod isalso driven into the ground and has four radials attached to itabout an inch and a half below ground level. A dipole -to-coaxconnector is connected between the bottom U -bolt whichsupports the radiator and the ground rod. This affords an easyarrangement for connecting the coax line. The radiator can beany size tubing you wish to use for operation on 10, 15 andeven 20 metres.
If you wish a very sturdy mount, the ground rod can be ametal fence post.
Furthermore the section of the 2" x 3" or 2" x 4" battenbelow the vertical radiator can be bolted to the metal fencepost. Separation can be such that the dipole connector can bespanned between radiator U -bolt and the bolt that fastens thewooden support to the metal fence post. In our own applica-tion the radiator was a two -section TV mast that would permitoperation on either 15 or 20 metres because it could betelescoped. This latter method of assembly was helpful in con-structing the vertical beams for 15 and 20 metre operationthat will be covered later. For 10 and 15 metre operation, twotelescoping sections of smaller diameter tubing were used.Shop around at flea markets and surplus outlets, or any place
41
metal tubing is sold, to find a proper combination.
21. TELESCOPING VERTICALS
As mentioned in the previous discussion the ability totelescope your vertical permits operation on more than oneband. Two 10 -foot telescoping sections provide an easy meansof changing over your vertical between 10 and 15 metreoperation, Fig.21. A 5 foot and 7 foot section provide an easymeans for 10 and 15 metre changeover.
To maintain good connections make certain you have asnug fit and a good low -resistance connection where the innertube leaves the outer tube. If you wish you can drill bolt holesthrough the two conductors when the two desired resonantlengths are found.
22. UMBRELLA VERTICALS
Telescoping TV masts function well as vertical quarter-waveson 40, 80 and 160 metres. A four -section mast can beextended to the approximate 33 feet needed for 40 metreoperation. The same size mast can also be used on 80 metresby using aerial wire to extend its resonant length as shown inFig.22. The four -section mast can be extended to at least 36feet. Approximately 24 foot lengths of an aerial wireconnected to the top can produce 80 -metre resonance. Threelengths of aerial wire can be made to extend away from thetop and then supported at ground level using nylon rope. Suchan arrangement performs very well and matches ideally to50 -ohm coaxial line. For best low -angle results use about9 quarter -wave radials stretched out about 2 inches beneaththe surface. Using a 50 -foot telescoping mast fine results wereobtained on 160 metres with umbrella aerial wires about 80foot long. In all of these umbrella installations it may be neces-sary to adjust the umbrella wire length to find resonance at apreferred frequency. However, performance is quite widebandonce you get the resonant length into the band.
42
1
I
16' max(20)
-
11'(15)
10'
Fig. 21. Telescoping verticals
T--- 11' max(15;
5'
il- 8'2"(10)
1r 4
7'
The base of the vertical was mounted in a wood/cementform and supported by appropriate nylon rope guys. Thismight be frowned upon as a base insulator. However, it is aneconomical arrangement and performance was fine. A metallicstrap was used to attach the coax connector to the bottom ofthe vertical while a stiff wire connected the shield side of thecoax connector to the radial system.
43
Ae-ial wiresspace 120°
Insulator
aW
Concrete
TelescopingTV mast
Groundlevel
Radials
Fig. 22. Umbrella vertical
23. PHASED VERTICALS
The quarter -wavelength verticals described previously can beconnected into a variety of directional phased combinations.These combinations produced some surprising DX resultsdespite the fact that they were ground -mounted. Variousbroadside and end -fire arrangements can be set-up as shown in
44
Fig.23. In example (i), the two verticals are fed in -phase froma centre junction to which the transmission line is attached.A T -junction is convenient. The in -phase connection of thetwo verticals set up a figure -eight broadside pattern. The two -element combination is bi-directional perpendicular to theplane of the two aerials.
By feeding the two verticals end -fire, the bi-directionalpattern can be along the line of the two aerials as shown inexample (ii). In this phasing arrangement the one aerial is fedwith the transmission line while the second by a half -wavelengthsection of line that runs between the first and second verticals.Since your verticals are mounted at ground level it is con-venient to change over the directional pattern wheneverdesired.
Example (iii) shows a 90 -degree end -fire connection withthe two radiators separated by a quarter -wavelength or 90degrees. Since the second radiator is fed 90 degrees lagging thefirst radiator by the 90 degree section of interconnecting line,a cardioid pattern in the direction of the lagging radiator isset-up. This arrangement was described previously in conjunc-tion with the coverage of horizontal phased arrays.
Example (iv) shows how the cardioid pattern can bereversed by using an intervening section of coax line that isthree-quarter wavelength long. By so doing, radiator 1 lagsradiator 2 by 90 degrees. Dimensions are given for 15 metreoperation. Four resonant radials are used. In mounting theradials do not permit the radial for radiator 1 to touch theradial of radiator 2.
In using two element phased verticals, particularly whenyou plan them to permit change in the directional pattern, itis advisable to use a tuner to insure optimum transmitterloading.
24. TWO -ELEMENT BROADSIDE
Two practical broadside verticals with dimensions for 20 and40 metre operation are given in Fig.24. In this arrangementcentre feed was used to obtain an in -phase feed. It is true that
45
-t. c
12la
gs I1
, by
90
(iii)
End
fire
, 90
Fig,
23(
h)
kilF
-1/4
1/4
X10
'11"
1/4
X r
eson
ant r
adia
ls11
'2"
(iv)
15 M
eter
end
fire
1/2
X34
'8"
1/4X
1/4X
16'6
"16
'6"
T-ju
nctio
n
1/4A
rad
ials
16'9
"
(i) 2
0 M
eter
bro
adsi
de
Fig.
24(
a) T
wo-
elem
entb
road
side
1/4X
rad
ials
16'9
"
Fig.
24(
b)
1/4
X32
'4"
1/2
Xi
68'4
"
1/4
X37
'4"
1/4
Ara
dial
s32
'8"
Tra
nsm
itter
IT
uner
(ii)
40 M
eter
bro
adsi
de
1/4X
radi
als
32'8
"
matching is not ideal but reasonable results were obtainedusing a tuner ahead of the transmitter. The use of resonantradials do keep up the impedance of each of the quarter -waveverticals. Respective radials of the two verticals should nottouch each other. If you are concerned about the matching atthe T -junction 3/4 wavelength sections of line can be usedbetween each radiator and the T -junction. Use 70 -ohm line forthese two segments. The coaxial line back to the transmittershould be 50 -ohm line.
25. END -FIRE BROADSIDE COMBINE
The arrangement of Fig.25 demonstrates how to constructindividual phasing loops that can be inserted to alter theradiation pattern of two quarter -wavelength verticals separatedby something less than a half -wavelength. Good broadside andend -fire 180 degree patterns are obtained, while the end -fire
90 degree pattern is acceptable but not ideal. Example (i)shows the broadside configuration with dimensions' given for15 metre operation. Proper lengths of feed cable after the T -junction permit end -fire 90 degree unidirectional operation.Compare (ii) and (iii) to show how the unidirectional patterncan be reversed using the same pre-cut feed cable. Example (iv)shows the end -fire 180 degree cabling. This combination feedsthe two verticals out -of -phase and a bi-directional pattern is set
up in line with the two verticals. Recall that the broadsidepattern of example (i) is perpendicular to the plane of the two
verticals.Some helpful dimension tables follow. Have a good time
with your antenna experiments!
50
(i) 15 Meterbroadside
1/4 A10'11"
1/4 A radials11'2"
(ii) End-fire 90*
.1111111 -
(iii) End-fire 90°
.111111.
(iv) End-fire 180'
1.4* -_<1/2 X_Iopi15'3"
7'71/2" 7'71/2"
1/4 A10'11"
1/4 A radials11'2"
-0.
Fig. 25. End-fire broadside combine
51
DIMENSION TABLES
The following tables supply important data useful in thepractical dimensioning in feet of aerial systems 2 through160 metres including the new WARC bands. Dimensions aregiven for the UK 4 metre band and the USA 6 metre band.A full range of dimensions are given for the 40 and 80 metrebands to accommodate the UK bands as well as the widerUSA bands.
Column 1 gives the frequency in MHz. Columns 2 and 3show the Y4X and la free space dimensions in feet. This datais helpful in spacing beam elements, both parasitic and phasedarrays. Column 4 is the length, in feet, of each quarter -waveside of a dipole. Column 5 is the length, in feet, of a three-quarter side of a 3/2 wavelength aerial. Columns 6 and 7 showthe parasitic reflector and director length in feet for beamaerials. Column 8 gives the dimensions, in feet, for the full -wave triangle. Columns 9 and 10 show the length, in feet, of%X and %X segments for the common 0.66 velocity factorcoaxial line. In using phasing and matching stubs made ofcoaxial line the velocity factor must be considered.
53
Freq
.M
Hz
2
YiX ft.
3
ft.
4
Dip
ole
Aft
.
5
ft.
6
Ref
l.ft
.
7
Dir
.ft
.
8
ft.
9
Y1X
0.66
10Y
dk
0.66
1.81
1.82
1.83
1.84
1.85
1.86
1.87
1.88
1.89
1.90
1.91
1.92
1.93
1.94
1.95
1.96
1.97
135.
913
5.2
134.
413
3.7
133.
013
2.3
131.
613
0.9
130.
212
9.5
128.
812
8.1
127.
512
6.8
126.
212
5.5
124.
9
271.
827
0.3
268.
826
7.4
266.
026
4.5
263.
126
1.7
260.
325
8.9
257.
625
6.3
254.
925
3.6
252.
325
1.0
249.
7
129.
312
8.6
127.
912
7.1
126.
512
5.8
125.
112
4.5
123.
812
3.2
122.
512
1.9
121.
212
0.6
120.
011
9.4
118.
8
160
ME
TR
ES
392.
339
0.1
388.
038
5.9
383.
838
1.8
379.
737
7.7
375.
737
3.7
371.
736
9.8
367.
936
6.0
364.
136
2.2
360.
4
271.
827
0.3
268.
826
7.4
266.
026
4.5
263.
126
1.7
260.
325
8.9
257.
625
6.3
254.
925
3.6
252.
325
1.0
249.
7
248.
624
7.3
245.
924
4.6
243.
224
1.9
240.
123
9.4
238.
123
6.8
235.
623
4.4
233.
223
1.9
230.
122
9.6
228.
4
543.
654
0.7
537.
253
4.8
531.
952
9.0
526.
252
3.4
520.
151
7.9
515.
251
2.5
509.
150
7.2
504.
650
2.0
499.
5
89.5
89.0
88.5
88.0
87.6
87.1
86.6
86.2
85.7
85.3
84.9
84.4
83.9
83.5
83.1
82.7
82.2
179.
017
8.0
177.
017
6.1
175.
117
4.2
173.
317
2.3
171.
417
0.5
169.
616
8.8
167.
916
7.0
166.
116
5.3
164.
5
1.98
124.
224
8.5
118.
235
8.6
248.
522
7.3
497.
081
.816
3.6
1.99
123.
624
7.2
117.
635
6.8
247.
222
6.1
494.
581
.416
2.8
80 M
ET
RE
S
3.52
69.9
139.
866
.520
1.7
139.
812
7.8
279.
546
.092
.03.
5469
.513
9.0
66.1
200.
613
9.0
127.
127
8.1
45.8
91.5
3.56
69.1
138.
265
.719
9.4
138.
212
6.4
276.
445
.591
.03.
5868
.713
7.4
65.4
198.
313
7.4
125.
727
4.8
45.3
90.5
3.60
68.3
136.
765
.019
7.2
136.
712
5.0
273.
345
.090
.0L
A3.
62(.
..,68
.013
5.9
64.6
196.
113
5.9'
124.
327
1.8
44.7
89.5
3.64
67.6
135.
264
.319
5.1
135.
212
3.6
270.
344
.589
.03.
6667
.213
4.4
63.9
194.
013
4.4
122.
926
9.8
44.3
88.5
3.68
66.8
133.
763
.619
2.9
133.
712
2.3
267.
444
.088
.03,
7066
.513
3.0
63.2
191.
913
3.0
121.
626
5.9
43.8
87.6
3.72
66.1
132.
362
.919
0.9
132.
312
1.0
264.
543
.587
.13.
7465
.813
1.6
62.6
189.
813
1.6
120.
326
3.1
43.3
86.6
3.76
65.4
130.
962
.218
8.8
130.
911
9.7
261.
743
.186
.23.
7865
.113
0.2
61.9
187.
813
0.2
119.
026
0.3
42.9
85.7
3.80
64.7
129.
561
.618
6.8
129.
511
8.4
258.
942
.685
.33.
8264
.412
8.8
61.3
185.
812
8.8
117.
825
7.6
42.4
84.8
3.84
64.1
128.
160
.918
4.8
128.
111
7.2
256.
342
.284
.4
0"
1
Freq
.M
Hz
2X
IX ft.
314
X
ft.
4D
ipol
eW
t.
534
X
ft.
6R
efl.
ft.
7D
ir.
ft.
8T
ri.
ft.
%X
X0.
66
10
0.66
3.86
63.7
127.
560
.6'1
83.9
127.
511
6.6
254.
942
.083
.9
3.88
63.4
126.
860
.318
2.9
126.
811
6.0
253.
641
.883
.5
3.90
63.1
126.
260
.018
2.0
126.
211
5.4
252.
341
.583
.1
3.92
62.8
125.
559
.718
1.1
125.
511
4.8
251.
041
.382
.7
3.94
62.4
124.
859
.418
0.2
124.
811
4.2
249.
741
.182
.2
3.96
62.1
124.
259
.117
9.3
124.
211
3.6
248.
540
.981
.8
3.98
61.8
123.
658
.817
8.4
123.
611
3.1
247.
240
.781
.4
40 M
ET
RE
S
7.02
35.0
70.1
33.4
101.
170
.164
.114
0.2
23.1
46.2
7.04
34.9
69.9
33.3
100.
869
.963
.913
9.8
23.0
46.0
7.06
34.8
69.7
33.2
100.
669
.763
.713
9.4
22.9
45.9
7.08
34.7
69.5
33.1
100.
369
.563
.513
9.0
22.9
45.8
7.10
34.6
69.3
33.0
100.
069
.363
.413
8.6
22.8
45.7
7.12
34.5
69.1
32.9
99.7
69.1
63.2
138.
222
.845
.5
7.14
34.5
68.9
32.8
99.4
68.9
63.0
137.
822
.745
.4
7.16
34.4
68.7
32.7
99.2
68.7
62.8
137.
422
.645
3
7.18
34.3
68.5
32.6
98.9
68.5
62.7
137.
022
.645
.1
7.20
34.2
68.3
32.5
98.6
68.3
62.5
136.
722
.545
.07.
2234
.168
.132
.498
.368
.162
.313
6.3
22.4
44.9
7.24
34.0
68.0
32.3
98.1
68.0
62.2
135.
922
.444
.87.
2633
.967
.832
.297
.867
.862
.013
5.5
22.3
44.6
7.28
33.8
67.6
32.1
97.5
67.6
61.8
135.
222
.344
.5
20 M
ET
RE
S
14.0
217
.535
.116
.750
.635
.132
.170
.211
.623
.114
.04
17.5
35.0
16.7
50.5
35.0
32.1
70.1
11.5
23.1
14.0
617
.535
.016
.650
.535
.032
.070
.011
.523
.014
.08
17.5
35.0
16.6
50.4
35.0
32.0
69.9
11.5
23.0
14.1
017
.434
.916
.650
.434
.931
.969
.811
.523
.014
.12
17.4
34.8
16.6
50.3
34.8
31.9
69.7
11.5
23.0
14.1
417
.434
.816
.550
.234
.831
.869
:611
.522
.914
.16
17.4
34.7
16.5
50.1
34.7
31.8
69.5
11.4
22.9
14.1
817
.334
.716
.550
.134
.731
.769
.411
.422
.914
.20
17.3
34.6
16.5
50.0
34.6
31.7
69.3
11.4
22.8
14.2
217
.334
.616
.549
.934
.631
.669
.211
.422
.814
.24
17.3
34.5
16.4
49.9
34.5
31.6
69.1
11.4
22.8
14.2
617
.334
.516
.449
.834
.531
.669
.011
.422
.714
.28
17.2
34.5
16.4
49.7
34.5
31.5
68.9
11.3
22.7
(.11 00
1
Freq
.M
Hz
2%
X
ft.
3X
ft.
4
Dip
ole
'aft
.
5
3/X
ft.
6R
efl.
ft.
7D
ir.
ft.
8T
rL ft.
9Y
IX
0.66
10'W
\0.
66
14.3
017
.234
.416
.449
.734
.431
.568
.811
.322
.7
14.3
217
.234
.416
.349
.634
.431
.468
.711
.322
.6
14.3
417
.234
.316
.349
.534
.331
.468
.611
.322
.6
15 M
ET
RE
S
21.0
211
.70
23.4
111
.13
33.7
823
.41
21.4
146
.81
7.71
15.4
1
21.0
611
.68
23.3
611
.11
33.7
123
3621
.37
46.7
27.
6915
.38
21.1
011
.66
23.3
211
.09
33.6
523
.32
21.3
346
.64
7.68
15.3
6
21.1
411
.64
23.2
711
.07
33.5
923
.27
21.2
946
.55
7.66
15.3
3
21.1
811
.61
23.2
311
.05
33.5
223
.23
21.2
546
.46
7.65
15.3
0
21.2
211
.59
23.1
911
.03
33.4
623
.19
21.2
146
.37
7.63
15.2
7
21.2
611
.57
23.1
411
.01
33.4
023
.14
21.1
746
.28
7.62
15.2
4
21.3
011
.55
23.1
010
.99
33.3
323
.10
21.1
346
.20
7.61
15.2
1
21.3
411
.53
23.0
610
.97
33.2
723
.06
21.0
946
.11
7.59
15.1
9
21.3
811
.51
23.0
110
.95
33.2
123
.01
21.0
546
.02
7.58
15.1
5
21.4
211
.48
22.9
710
.93
33.1
522
.97
21.0
145
.94
7.57
15.1
3
10 M
ET
RE
S
28.2
8.72
17.4
58.
3025
.17
I17
.45
15.9
534
.89
5.74
11.4
9
28.4
8.66
17.3
28.
2425
.00
17.3
215
.85
34.6
55.
7011
.41
28.6
8.60
17.2
08.
1824
.83
17.2
015
.73
34.4
15.
6611
3328
.88.
5417
.08
8.13
24.6
517
.08
15.6
334
.17
5.63
11.2
529
.08.
4816
.97
8.07
24.4
816
.97
15.5
233
.93
5.59
11.1
729
.28.
4216
.85
8.01
24.3
216
.85
15.4
133
.70
5.55
11.1
029
.48.
3716
.73
7.96
24.1
516
.73
15.3
133
.47
5.51
11.0
229
.68.
3116
.62
7.91
23.9
716
.62
15.2
033
.24
5.47
10.9
5
6 M
ET
RE
S
50.2
4.90
9.80
4.66
14.1
49.
808.
9619
.60
3.23
6.45
50.6
4.86
9.72
4.62
14.0
39.
728.
8919
.45
3.20
6.40
51.0
4.82
9.65
4.59
13.9
29.
658.
8219
.29
3.18
6.35
51.4
4.79
9.57
4.55
13.8
19.
578.
7519
.14
3.15
6.30
51.8
4.75
9.50
4.52
13.7
19.
508.
6919
.00
3.13
6.25
52.2
4.71
9.43
4.48
13.6
09.
438.
6218
.85
3.10
6.21
52.6
4.68
9.35
4.45
13.5
09.
358.
5618
.71
3.08
6.16
53.0
4.64
9.28
4.42
13.4
09.
288.
4918
.57
3.06
6.11
53.4
4.60
9.21
4.38
13.3
09.
218.
4318
.43
3.03
6.07
53.8
4.57
9.14
4.35
13.3
09.
148.
3618
.29
3.01
6.02
4 M
ET
RE
S
70.1
3.51
7.02
3.34
10.1
3I
7.02
6.42
14.0
42.
314.
62
rn
1
Freq
.M
Hz
2
%X
ft.
3
%X
ft.
4 Dip
ole
%V
t.
5
%?
ft.
6
Ref
1.
ft.
7
Dir
.
ft.
9
Tri
.
ft.
9
3 X
0.66
10
X
0.66
70.3
3.50
7.00
3.33
10.1
07.
006.
4014
.00
2.30
4.61
70.6
3.49
6.97
3.32
10.0
66.
976.
3713
.94
2.29
4.59
2 M
ET
RE
S
144.
41.
703.
411.
624.
923.
413.
126.
811.
122.
2414
4.8
1.70
3.40
1.62
4.90
3.40
3.11
6.80
1.12
2.23
145.
21.
693.
391.
614.
893.
393.
106.
781.
122.
23
145.
61.
693.
381.
614.
8833
83.
096.
761.
112.
23
146.
01.
683.
371.
604.
863.
373.
086.
741.
112.
22
146.
41.
683.
361.
604.
853.
363.
076.
721.
112.
21
146.
81.
683.
351.
594.
843.
353.
076.
701.
102.
21
147.
21.
673.
341.
594.
823.
343.
066.
681.
102.
20
147.
61.
673.
331.
594.
813.
333.
056.
671.
102.
20
NE
W W
AR
C B
AN
DS
30 M
ET
RE
S
10.0
224
.649
.123
.35
70.9
49.1
44.9
98.2
16.1
732
.33
10.0
424
.549
.023
.31
70.7
49.0
44.8
98.0
16.1
432
.27
10.0
624
.548
.923
.26
70.6
48.9
44.7
97.8
16.1
032
.20
10.0
824
.448
.823
.21
70.4
48.8
44.6
97.6
16.0
732
.14
10.1
024
.448
.723
.17
70.3
48.7
44.6
97.4
16.0
432
.08
10.1
224
.348
.623
.12
70.2
48.6
44.5
97.2
16.0
132
.02
10.1
424
.348
.523
.08
70.0
48.5
44.4
97.0
15.9
831
.95
17 M
ET
RE
S
18.0
813
.61
27.2
112
.94
39.3
027
.21
24.8
954
.42
8.96
17.9
218
.10
13.5
927
.18
12.9
339
.23
27.1
824
.86
54.3
68.
9517
.90
18.1
213
.58
27.1
512
.92
39.2
227
.15
24.8
354
.30
8.94
17.8
818
.14
13.5
627
.12
12.9
139
.21
27.1
224
.81
54.2
48.
9317
.86
18.1
613
.55
27.0
912
.90
39.2
127
.09
24.7
854
.18
8.92
17.8
4
12 M
ET
RE
S
24.9
29.
8719
.74
9.39
28.5
19.7
418
.06
39.4
96.
5013
.00
24.9
49.
8619
.73
9.38
28.5
19.7
318
.04
39.4
56.
5012
.99
24.9
69.
8619
:72
9:37
28.4
19.7
218
.03
39.4
26.
4912
.98
24.9
89.
8519
.71
9.36
28.4
19.7
118
.01
39.3
96.
4912
.97
LENGTH CONVERSION TABLE
The table below is an aid in converting feet in decimals todecimal inches and then to practical tape -lengths. For example,an element that is 31.5 feet is 31 feet 6 inches. An aerial whichis 12.35 feet is approximately 12' 41/4". These are not exactvalues but are practical in terms of cutting a length with a tapemeasure. Inches equals decimal part of a foot times 12.
Decimalft.
Decimalin.
Tapein.
.05 0.6 %
.10 1.2 11/4
.15 1.8 17/8
.20 2.4 2 3/8
.25 3.0 3
.30 3.6 3%
.35 4.2 41/4
.40 4.8 47k
.45 5.4 53/8.50 6.0 6.55 6.6 65/8.60 7.2 71/4.65 7.8 77/8.70 8.4 83/8.75 9.0 9.80 9.6 9%.85 10.2 101/4.90 10.8 107/8.95 11.4 113k
62
EQUATIONS
1/4X Free Space = 246/fmHz423942//fivifmilzz1/2X Free Space =
1/4X Dipole =3/4X Dipole = 710/fmHzReflector = 492/fmHzDirector = 450/fmHzTriangle = 984/fmHz%X x 0.66VF = 162/fmHz1/2X x 0.66VF = 324/fMHz
TYPES OF CABLES
Coaxial(RG 59U -58U)
Open wire(450a)
Fig. 26. Illustration of types of cables
Ribbon cable(30011)
63
ALSO OF INTEREST
BP105: AERIAL PROJECTSR. A.PenfoldWhether you have built a very simple short wave receiver or have pur-chased a most sophisticated piece of equipment, the performance youachieve will ultimately depend on the aerial to which your set is con-nected.
The subject of aerials is vast but in this book the author has con-sidered practical aerial designs, including active, loop and ferrite aerialswhich give good performances and are relatively simple and inexpensiveto build. The complex theory and mathematics of aerial design havebeen avoided.
Also included are constructional details of a number of aerial acc-essories including a preselector, attenuator, filters and tuning unit.96 pages 19820 85934 080 5' Z1.95
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160 Coil Design and Construction Manual£2.50227 Beginners Guide to Building Electronic ProjectsE1.96BP28 Resistor Selection HandbooxE0.611BP36 50 Circuits Using Germanium Silicon & Zener Diodes £1.95BP37 50 Projects Using Relays, SCRs and TRIACs£2.95BP39 50 (FET) Field Effect Transistor ProjectsE2.958P42 50 Simple LED Circuits Et%BP44 IC 555 ProjectsE2.95BP48 Electronic Projects for Beginners£1.95BP49 Popular Electronic Projects£2.50BP53 Practical Electron'. Caleuhrions & Formulae E3.9513P56 Electronic Security Devices£2.95BP74 Electronic Music ProjectsE2.95BP76 Power Supply Projects£2.50BP78 Practical Computer Experiments£1.75eno Popular Electronic Circuits - Book 1 £2.95BP84 Digital IC Projects£1.95ens International Transistor Equ'valents Guide £3.958P137 50 Simple LED Circuits- Book 2 £1.95ens How to Use Op -amps£2.95BP30 Audio Projects42.50BP92 Electronics Simplified- Crystal Set Construction E1.75EIP94 Electronic Projects for Cars and Boats£1.95B P35 Model Railway Projects£2.95BP97 IC Projects for Beginners£1.9513P98 Popular Electronic Circuits - Book 2 £2.95B P39 Mini -matrix Board Projects£2.50BP105 Aerial Projects£2.50BP107 30 So'dories, Breadboard Projects - Book 1 £2.95BP110 How to Get Your Electronic Projects WorkingE2.95BP111 AudioE3.95BP115 The Pre -computer Book£1.95BP118 Practical Electronic Building 3locks -Book 2 £1.95BP121 How to Design and Make Yoar Own PCB's £2.50BP122 Audio Amplifier Construction £2.95BP125 25 Simple Amateur Band Aerials41.95BP126 BASIC & PASCAL in Parallel £1.50BP130 Micro Interfacing Circuits - Book 1 £2.75P131 Micro Interfacing Circuits - Book 2 E2.75P132 25 Simple SW Broadcast Band AerialsE1.95P136 25 Simple Indoor and Window Aerials £1.75P137 BASIC & FORTRAN in Paralle Et%P138 BASIC & FORTH in Parallel E1.95P144 Further Practical Electronics Calculations & Formulae £4.95P145 25 Simple Tropical and MW Band Aerials E1.75P146 The Pre -BASIC Book £2.95P147 An Introduction to 6502 Machine Code £2.95P148 Computer Terminology Explained £1.95P171 Easy Add-on Projects for Amstrad CPC 464. 664. 6128 & MSS Computers 02.95P176 A TV-Okers Handbook (Revised Edition) E5.95P177 An Introduction to Computer CommunicationsE2.95P179 Electronic Circuits for the Computer Control of Robots £2.95P182 MIDI Projects£2.95P184 An Introduction to 68000 Assembly LanguageE2.95P187 A Practical Reference Guide to Word Processing on the Amstrad PCW8256 & PCW8512 £5.95P190 More Advanced Electronic Security Projects E2.95P192 More Advanced Power Supply Projects £2.95P193 LOGO for BeginnersE2.95P196 BASIC & LOGO in Parallel E2.96P197 An Introduction to the Amstrad PC'sE6.95P198 An Introduction to Antenna Theory£2.95P230 A Concise Introduction to GEM E2.95P232 A Concise Introduction to MS-DOS £2.95P233 Electronic Hobbyists Handbook £4.95P239 Getting the Most From Your Multimeter £2.95P240 Remote Control HandbookE3.95P243 BBC BASIC86 on the Amstrad PC's & IBM Compatibles- Book 1: Language £3.95P244 BBC BASIC86 on the Amstrad PC's & IBM Compatibles - Book 2: Graphics E3.95and Disk Files
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£4.95£3.95£3.95£4.95£4.95£4.95£4.95E4.95£4.95£3.95£4.95£4.95£4.95E3.95£4.95E4.95E4.95E5.95£4.95£4.95E4.95£4.95£4.95£4.95£5.950.95£5.95E5.95£5.95£4.95£5.95E5.95
25 SimpleAmateur Band Aerials
This concise book describes how to build 25 amateur band
aerials that are simple and inexpensive to construct andperform well. The designs start with the simple dipole andproceed to beam, triangle and even a mini -rhombic made from
four TV masts and about 400 feet of wire.
After the aerial discussion you will find a complete set ofdimension tables that will help you spot an aerial on a particu-
lar frequency. Dimensions are given for various style aerialsand other data needed for spacing and cutting phasing lengths.
Also included are dimensions for the new WARC bands.
£1.95
9 78
ISBN 0-8 59 34-100-=X0 0 19 5(!;0= ---
CO --
0859 341004