MY WIRELESS SET No 18 Mk3 AND ME
In a moment of madness (which is happening more often these days) I recently purchased a very old Wireless Set No 18, these old WW2 veterans carried a large portion of the British army forward communications during WW2 and were active in all areas of the world, Western Dessert, Far East and in Europe after D Day, I have no idea how they performed during their war time service as I had not been born then, I only arrived when hostilities were over as a twinkle in my Dads eye when he returned from the war after being demobbed.

The No 18 set and I do go back a long way though, when I first became interested in Radio Communication at the tender age of 14 these sets and many more like them were flooding the war surplus markets and were available for a couple of weeks pocket money, I'm afraid to say like many others I had no idea of any sort of conservation, they suffered all sorts of strange modifications at my hands and were eventually stripped down for spares which were used for other projects, other than a few midnight clandestine contacts with other likeminded radio mad individuals the transmitters were largely used for spares, much later when I became a licensed radio Ham I rapidly moved on to VHF and surplus PMR radios.
 
But I have always been a QRP operator at heart, mainly I suppose that I found in the UK high power meant high levels of TVI and the fallout from this from parents and later neighbours wasn't worth the hassle, and somehow a low power  CW contact using primitive equipment gave me a great deal of fun and satisfaction, now after retiring from a whole lifetime spent in electronic repairs in domestic and professional Communications I'm enjoying reliving those distant days of my education into electronic communication.

So this will be a project of discovery as well as nostalgia for me. Anyway below is the beast I purchased, usually these days these old sets go for meggabucks, over £300 or about $500 is not unusual, however this one had no valves (tubes) and it's condition is not wonderful so it was considerably cheaper, you can see a really nice one here, my one is below, it is basically complete but the interconnection plug and socket is missing also the battery socket and leads have been chopped off, the front panels have been painted and there is some globby soldering here and there mainly around the audio / BFO stage
So I have room to move as regards any modifications, I won't do any serious chopping, but maybe a couple of reversible mods to make it more usable for CW could be in order, Time now for an evaluation  on the possibilities. 3/11/08
At the moment of writing I have no Valves / tubes for it so I'm having to content with finding my way around and doing a bit of maintenance until they arrive, They are quite simple sets, rugged and reliable, I have few doubts about the transmitter, it is just an MO driving a PA to about 500mw, experience has taught me that half a watt will take me across the North Sea and into Europe on 40mtrs CW on a good day even further, the only doubts I have are with the stability of the MO at 7mhz, but with these really low power battery valves where heat is not really a problem drift will be minimal ( I hope) as to the receiver it is about as simple as it can be and still be useful, one RF amp, Osc, and one IF amp, and an audio stage that doubles as a BFO doubts are the usual of drift and the Audio / BFO sounds a bit tricky, again time will tell (can't wait to get those tubes)
First thing to do is to repair the Meter, below you can see the glass has pushed in and jammed the movement, this is very common on this old kit as the glue that held the glass in has dried up and turned to dust.
So first job is to take it to pieces and carefully clean it up and refit the glass with a modern adhesive, it is a fiddly little job, care must be taken not to damage the movement as it is VERY fragile, the dial face paint has cracked and crazed a bit but that doesn't matter, this project is a "Get it going and evaluate it" one, if  I'm really happy with it I may go further with spray jobs and re lettering etc
And now the next job is to find something to power it with, originally it ran from dry batteries all now long gone, it's requirements are about 3v DC for the indirect heaters and about 160v DC for the HT, and 12v + HT ?? this 12v + was a bit of a mystery but after studying the circuit for a while I found the 12v + is part of of the HT stack and it is indeed taken to -ve chassis so the HT -ve becomes a  12v negative bias line, I have various old PSU's left over from other projects so I can easily wire something up for test purposes, I have refitted the meter and connected 3v LT and after much cleaning of pins and large squirts of switch cleaning fluid into the switches the meter swung over to half scale the VERY first signs of life for probably over 50 years, next I connected about 150v of HT, this is a good test to see if there are any shorts or smoke signals, I don't intend to start changing components unless things don't work.
And above you can see the transmitter sitting on my workbench connected to a temporary PSU, bottom left hand side is the power plug with a crop of croc clip leads supplying the power, and on the front panel is a yellow croc lead simulating transmit mode, as this set switches from transmit to receive by just switching the  heater volts, simple but effective, for  CW the tx is switched on by a switch on the morse key and then the PA valve HT is keyed all very primitive which I really like, you can see the Meter registering volts, can't wait to get these valves
 
5/11/08 AT LAST!!! the valves have arrived, but sad to say one of the AR8's was defunct O/C heaters and the top grid connection broken, but I have enough to try out the receiver, I must admit the valves or tubes are where the magic is :) these old units are really just lumps of metal until you plug in the glow bugs, and then the magic works, only this time it didn't, only to be expected I suppose although I was a bit disappointed, I had just hooked up the receiver first and it was as dead as a doornail, but after taking a few meter readings I found that the grid bias was extremely high and then I realised what I had done, there were a couple of resisters in the Transmit chassis in a potential divider circuit that reduced the bias volts before they got to the receiver, and by bypassing the transmitter I had left them out, no problermo, I quickly wired up a couple on my temporary PSU and switched on, and YES loud hissing in the headphones, I connected a temporary antenna and she speaks!!!
A quick tune around and stacks of CW on 40mtrs but no BFO, the BFO is a weird one in this set, the Audio stage also doubles as a BFO when the AF gain is turned up but it is not working, I just knew I would have trouble with it, these odd little circuits are always trouble, so just for a temporary measure I used my signal generator set to 460khz as a BFO and the receiver works really well!!! and seems quite stable!! as long as you don't go near the oscillator coil,  It seems to be begging for some sort of RF gain control, I may fit something on this grid bias circuit which will be external to the receiver, the transmitter is just supplying the tuned circuit for the receiver front end at the moment, time to relax for a while and play with it, before trying to find out what's wrong with the BFO below is my bench with all the temporary hook ups (so much for wireLESS)
I always work in a mess hi!! bottom right you can see where I started off well with a stabilised 3v heater supply the five diodes you can see in a ring are power diodes that have a forward zener voltage of .7v  five of those =3.5v  so if the LT psu shorts out and puts more than 3.5v DC on the heaters of my tubes it blows the fuse, real crowbar protection :) The PSU in the middle is the HT supply, the transformer is 240v AC primary with a 115-0-115 secondary, I have just used one half of the secondary 115 with a full wave bridge  and get a nice 150v DC, I'm using switch mode type for smoothing caps they are simply amazing 180uf at 400v only 1 inch long and as tough as old boots, so far so good :()
 
6/11/08 Well I spent all day today trying to get the BFO working on this radio, it had been quite badly got at which is a bad sign, lots of globby solder joints around the circuit, as I said previously this BFO is a real weird one, it uses the audio output valve as a colpitts oscillator as well, but to get the oscillator running you have to turn up the audio gain control!! obviously this was an afterthought as the original Mk1 was AM phone only, after checking I found that the core was missing on the oscillator coil and it wasn't an ordinary core either as the ones I tried would not work, I had to make a sort of plastic threaded rod and mount a ferrite core on the end to tune it to resonance at 465khz, and change the old wax caps to get it to finally fire up, but even then it was not much good, for a start I had to have the audio up fairly loud before the oscillator would fire up, and this crazy situation seems as it should be according to the manual!! also with heavy audio bursts the oscillator would shift frequency or stop working and there was hardly enough injection to be really useful, the problem is really and truly the BFO on this radio is not fit for purpose, by injecting a signal from my little transistor signal generator it becomes quite a useful little 40metre CW  receiver, SO where to go from here, do I give in and add a little transistor 465 khz BFO inside? also the receiver has one heck of an AGC system, and it really needs some sort of RF gain control as a really strong signal a few khz away from a weak signal kills it stone dead, I'm on this slippery slope again trying to use old military kit over 60 years old as is, I mean can you say you are using an old 18set on air, when you have modified it, if only slightly? it is a tricky one, I know some guys who say they are using old military kit often are only using the transmitter, a modern receiver taking the job of the vintage one, but at the end of the day I'm using modern components in the power supply and will no doubt use an external audio filter when receiving so where does it stop. as it is I'm going to have to change the 5pin plug and socket that joins the sets together with a modern one as that is missing, maybe time to consolidate and tidy up the PSU join the sets together with a new plug and socket and have a long hard think, I haven't even got to the transmitter yet, I wonder what horrors lay in wait there :() anyway nobody said it was going to be easy, comments always welcome (Although comments referring to the loading up of dustbins I can do without :) but it is nice sitting here listening to the old beast chattering away on 7.03 QRP channel after all the years of silence, I can't help wondering about it's history and all the old ops that may have used it, I must say it looks very well used, ten out of ten for nostalgia :)
THE TRANSMITTER
7/11/08  I've spent today firing up the old transmitter, after lots of switch cleaning I plugged in the Tubes AND nothing :(( so putting my disappointment to one side I started making a few checks around the MO, it all looked ok just that the Tube didn't seem to be taking any current,   my replacement AR8 had arrived in the post and I had just plugged it in, surely it couldn't be faulty not another one, and yes after a few checks I found although the heaters were there they were only drawing half the current that they should, I think these old tubes are reaching the end of the line maybe some sort of age degradation, anyway I took the one out of the receiver that I knew was ok and tried again, this time it squeaked into life, first thing I noticed that the regulation on my PSU was rubbish, with huge swings in voltage, so time off to rebuild that, heavier choke and a fixed load in place all the time, time to try again, after a bit of hassle with the PA tuning I managed to squeeze nearly 1 watt out on CW, but what a chirp!!!! I rather like a little chirp as it attracts the ICOM and Kenwood specialists as they queue up to give a T7 report   also a chirp heard on CW these days means it is something unusual like vintage military or Homebrew, however this one is taking chirps a bit to far, Now the WS 68  is almost the same as the WS 18 being a lower band AND it had a Crystal socket, so just for a test I thought I might try the same idea on this 18 set  I coupled a 7.030 mhz QRP rock across the MO tuning cap and what a difference a lovely T9 note, and it works out well as the MO tuning cap swings the xtal quite a bit which is handy, as I've found just running a few hundred htz high or low of the QRP frequency often brings results.
Below you can see the old Transmitter under test, and below that you can just see just under one watt registering on my old Power meter and 7.03 or thereabouts on my frequency counter
 
 
So here we are, the evaluation of my 18 set is more or less complete, I should say that there may well be 18 sets out there that are in better condition and work better than my one but I suspect they are all fairly similar, As a set for for working CW on today's 40mtr amateur band it obviously could be done, although I think some small modifications are in order if I want to do this on a regular basis, the receiver really needs a better BFO and some sort of gain control, this could be done very easily by using one of these BFO kits sold by Walters and Stanton, the original circuitry can be left in place for any future restoration as the days of chopping these old sets to bits should be over, after all we are only temporary custodians, and the RF gain could be done using the 12v bias line with perhaps a couple of links inside the set to redirect the bias from the audio stage, the transmitter could be used as is but again I think xtal control is the answer really, again an xtal holder could be soldered inside the MO screened box or even a couple of small holes for a holder on the front panel like the 68 set so I can plug different ones in easily, depends on the ethics :) I have not tried the AM side of things yet as that doesn't really interest me, although thinking about it that side of things would work perfectly well without any modifications at all, if ever I wanted to use it on some sort of AM military net.

I can see all re sprayed and relabelled a few little reversible mods  a mains power supply I could have great fun with this little set, whether in all honesty I could say I'm using a WS 18 I'm not sure, jury still out on that one, so it is at this point where I have to make some serious decisions, how far do I go, I have to face the facts, although the basics of this old unit are still in place a lot of it isn't, all the original battery interconnection plugs and sockets are long gone, the leads that are left are in bad shape and likely to short out if moved about to much, I'm not really into collecting this old kit just to look at, I want to use it and try to recapture some of the old glory days, but I don't want to destroy its originality,  it wouldn't be practical to run it on batteries so (1) a tailor made Mains PSU is a must  that is the first job, then (2) some major re wiring of new leads plugs and sockets, then (3) a couple of small sockets for 10xj crystal operation  from the front panel just like the 68 set, that should conclude the transmitter, next (4) tidy the receiver and remove the HT current switch by just undoing the threaded ring and leaving it inside (just in case a future owner wanted to restore to original) and in its place fit an RF gain control, I have some ideas for this so I shall have to do some experimenting, and then (5) a new BFO, I rather fancy the BFO kit mentioned earlier, as it would be small and easy to fit and just as easily removed at a later date, it is giving into modern technology a little but it will make the receiver really useable for CW where at the moment it isn't, if all that pans out ok and it works well and I feel comfortable with it I may re spray the whole thing and re letter it, looks like another long term project. 12/11/08

:So  time now to start putting everything together    Thanks to VMARS for the Manuals and circuits
Next comes "Chassis Bashing" making the Power Supply chassis
G3YUH