Nowadays, manymedium-to-higherpriced AmateurRadio transceiverscome already fitted

with automatic antenna tuningunits (a.a.t.u.s) and frompersonal experience Ican tell you that theywork very well.Indeed, I feel that - forsafety’s sake - the man-ufacturers often tend toplay down the wide rangeof impedances the a.a.t.u.can match. But as I’ve been toldon many an occasion ... better safethan sorry!

And when it comes to oldertransceivers it’s become increasing-ly evident that many of you stillcherish older non a.a.t.u fittedequipment. So, with that in mind Ithought it would be an excellenttime to look at a possiblea.a.t.u. suitable for olderrigs, which at the sametime could be classed as aninvestment for newerequipment later on.

I mention ‘investment’because it’s inevitable that‘add-ons’ can appear to bequite expensive - especiallywhen you consider the‘trade in’ price (comparedto the value given to theequipment by the proudowner). My own recentlyacquired Digital SignalProcessing (DSP) unit - theW9GR DSP III is just suchan example.

Reviewed by yours trulyin 1999, a new DSP III wasnot available after I wrote agood review because toomany readers had boughtthem! However, ‘BargainBasement’ came to my res-

cue and Arthur Tait GM3LBE soldme his unit. However, althoughworking well, the DSP III is probablyworth half the value of some of myolder transceivers.

Despite the apparentexpense, once you have

got a non type specific‘add-on’ - with carefulplanning it can beused with whatevertransceiver you have

in your shack. So, I askyou to take my advice

seriously -forget the ‘com-mercial’ value of your older rig ifyou still enjoy using it and want toadd even more to your enjoyment

by purchasing or building (via kits)a modern ‘add on’ unit - do so. Ihave ...and I’m not regretting mydecision.

What’s On Offer?So, if you are considering someform of ‘add-on’ a.a.t.u. what doesthe SGC-237 PCB Coupler have tooffer us? Well in answer the ‘237 sa complete a.a.t.u., ready built ona printed circuit board (p.c.b.) andready to go - minus the case.

Assembled on a p.c.b. measuringonly 5 x 5.3in, the unit provides acompletely automatic tuningprocess for a variety of antennas.These include the following: Whips,Backstay (marine, sail) centre feddipole, dipole with line feed, Loop(small 2 x 2 turns), loop (large) 10ftand upwards, single turn, long wireand ‘ladder’ (open feeder’.

Rob Mannion

G3XFD asks

“Considering

adding an

automatic antenna

tuning to your

favourite older rig”?

If you are, Rob

suggests you may

like to consider the

‘add on’ a.a.t.u.

printed circuit board

unit from SGC

which he’s been

evaluating.

Cost: £199.95

Company: Waters & Stanton PLC

Contact: Sales

Tel: (01702) 206835

Website: www.wsplc.com

Rob Mannion G3XFD suggests you may like to consider

the ‘add on’ a.a.t.u. printed circuit board unit from SGC

Rob Mannion G3XFD has been theEditor of PW for over 11 years. He’s akeen ‘portable’ operator on both the

h.f. and v.h.f. bands

Automatic Antenna Tuner UnitThe SGC-237 PCB

ADDING AN EXTRA? – TRY THE SG-237 FOR SIZE!

Practical Wireless, January 2001 45

The SG-237 automatic antenna tuning

unit is small enough to be fitted inside

many transceivers. It could prove to be

useful if you’re considering installing an

‘add on’ a.a.t.u.

SGC Review A/w/Jan 28/11/00 10:44 am Page 45

The frequency coverage of theSG-237 ranges from 1.8 to60MHz. The quoted input imped-ance range is from 45 to 55Ω.

In use the a.a.t.u. requires aminimum r.f. input of 3W (p.e.p.)and can handle up to 100Wp.e.p. However, on c.w. there’s apower input limit of 40W(although the SGC manual doesnot state whether this is 40W d.c.input or 40W p.e.p.).

Usefully, the SG-237 can beoperated directly from the nowstandard 13.8V d.c. suppliesfound on Amateur Radio equip-ment. Average current require-ments are 300mA and the unitwill operate on voltages between10.5 and 18V d.c.

In use the SG-237 has anunlimited number of ‘memory’channels although in practice themanual states that there are: 168‘revolving’ memories’ available. Inpractice, from my experience ofusing these units this means thatthe a.a.t.u. will ‘remember’ thetuning combinations required forup to 168 ‘spot frequencies’before it has to work out therequirements again, with the mini-mum time being taken to do so onnumber ‘169’.

The SGC manual states that the‘random’ (frequency) set time istypically “less than two seconds”,with “re-current set time” (in otherwords - back to a frequencywhich has been used beforehand)as less than 10 milliseconds.

The SG-237 p.c.b. unit onlyweighs around 570gm (approxi-mately 1.25lbs) and can be oper-ated in any position. Operatingtemperatures are quoted as beingwithin the range of -35° to +75°C.

Practical ExperienceThe only really valid method toevaluate this sort of ‘add-on’ unitis to try it out ‘in the field’ gainingpractical experience. Well,although I did venture outside ...Ididn’t literally end up in the field -I just parked next to one in mycar!

To be honest, I did use the SG-237 at home, operating it in con-junction with a selection of trans-ceivers, and the very low mount-ed single wire antenna I have touse at my temporary home. This,in effect, can just be called a ‘long

wire’ for the 7MHz band. Despitethis I’ve had some good contactsusing it, even though it’s only 4mabove the ground.

At home I found the unit to beextremely effective and veryquick. I didn’t time it in operationbut I think it’s very unlikelyindeed that the SG-237 took morethan two seconds to tune theantenna - it seemed much less!

However, operating as a ‘bare‘chassis’ p.c.b. unit (as supplied) Imust again be honest and say thatby no stretch of the imaginationcould the SG-237 be described as‘silent’ in operation. It certainlyisn’t - the click-clack of the relayssee to that!

Sound level comparison: I wasrather stuck for a suitable compar-ison regarding the sound level ofthe relays on the a.a.t.u. After agreat deal of thought I considerthat the noise level can be com-pared to half a dozen small coinsin a trouser pocket ‘clicking’ andjingling together. But bear in mindthat whereas coins jingle everytime you walk - the a.a.t.u. soonstops clicking.

Despite the clicking of therelays as the a.a.t.u. works to findthe best combination of L and Cto match the antenna -it’s fascinat-ing to watch and it’s also quick.Additionally, once mounted in asuitable metal case I don’t thinkmuch, if any, sound wouldescape.

Personally, I feel that a largerdie-cast aluminium case (similarin fashion to the well known‘Eddystone’ boxes) would be idealto house the SG-237. In fact, apartfrom screening the mechanicalsounds - if buying one of theseunits for myself - I would invest ina die-cast box to provide radiofrequency (r.f.) screening.

I suggest using the SG-237 unitmounted in a screened metal boxbecause on several occasions Ifound that r.f. was affecting theswitching on the a.a.t.u. The prob-lem was only intermittent, andthen it was only a fleeting hesitan-cy on the ‘237 which drew myattention to the fact that r.f. (most-ly s.s.b.) was getting into the oper-ating side of the unit.

The problem only occurred on3.5 and 7MHz, and then only onspeech peaks. It lead the SG-237to momentarily re-tune the anten-

na. This only took a second or sobut was disconcerting.

However, when you considerthat for most of the time the SG-237 will be operating long wire orend-fed antennas - it’s not unrea-sonable to expect a certainamount of r.f. at the operating end.Even with a good r.f. ‘ground’ Ithought it best to place the SG-237 in an old Eddystone alumini-um box.

As an inveterate buyer of die-cast enclosures ‘just in case’ atrallies and junk sales - I had onewhich was just right! Onceinstalled in a box the unit waswell and truly screened, but evenin a small biscuit tin it receivedenough r.f. screening!

On The AirOperating ‘portable’ from my car Iused a selection of antennas,including a random long wire ofaround 20 metres in length, inassociation with a ground stakewhich I now carry. I also usedsomething new - one of theincreasingly popular fibreglass tele-scopic fishing rod antennas (usedwith a wire to provide a verticalantenna) which extend out to 10metres and this proved outstand-ingly successful. Using theportable equipment set-up which iswell known to PW readers - minusmy manual antenna tuning unit - Iwas soon working all over Europeon s.s.b. and c.w. Sitting in its tem-porary screened aluminium alloybox the SG-237 worked exception-ally well and very quickly indeed (Icould just about hear the relaysticking away as it worked). It soonprovided a good match on all thefrequencies I tried on 3.5, 7, 10,14, 18, 21 and 28MHz. (No activi-ty heard on 1.8MHz or 24MHz).

Intrigued, I also tried to loadone of my mobile whips (my18MHz whip) onto 50MHz. Itworked! - and although I didn’tget a QSO I heard a repeater andwas able to access it okay. Quitea surprise too!

However, the outstanding suc-cess proved to be when I used theSG-237 with my new fishing rodantenna. It was a joy to use and Ihad long QSOs with Canada,West Coast USA and South Africa.Not bad for 50W (s.s.b.) and 10Won c.w. eh? PW

46 Practical Wireless, January 2001

ADDING AN EXTRA? - TRY THE SG-237 FOR SIZE.

PLEASE MENTION THE PW REVIEW WHEN CONTACTING WATERS & STANTON. PW

Product

Pros & Cons

Pros: The SG-237 is very convenient

to mount on a board and I

found the unit to be extreme-

ly effective and very quick

when in use.

Cons: I must again be honest and

say that by no stretch of the

imagination could the SG-237

be described as ‘silent’ in

operation. It certainly isn’t -

the click-clack of the relays

see to that!

My thanks for the loan of

the SG-237 unit go to

Waters & Stanton, of 22

Main Road, Hockley, Essex

SS5 4QS. Tel: (01702)

206835, FAX: (01702)

205843.

The SGC-237 PCB Automatic

Antenna Tuner Unit

Summary

RRP:£199.95

So, would I consider buying a SG-

237 to use with my portable oper-

ating station? The answer is ‘Yes’ -

and it would be very convenient to

mount on the board I’ve got my

exisiting transceiver set-up fixed

onto, with no bother at all.

Finally, for wheelchair bound (and

those like me who aren’t able to

get in and out of the car/caravan

very easily) the SG-237 would be

extremely useful. I think it’s really is

worth considering the idea.

SGC Review A/w/Jan 28/11/00 10:44 am Page 46