About Leighton Davies

Licensed July 1971 as GW8EYG, mostly on 2M SSB, Always into radio and electronics thanks to my father GW3FSP, Managed to re-activate his callsign when Ofcom removed the morse requirment. Since then been active all bands up to 13cm.

Eliminating the VRC 353 Fan Noise


The VRC 353 is a very capable, fifty watt FM Transceiver designed and built by the military for use during the cold war. Its main use was in armoured and soft skinned vehicles and it provides FM Voice and Digital Operations from 30 to 76 Mhz in various configurations at ranges up to 50Km.


Its design makes it less than ideal for use in the average amateur shack – having been designed to withstand the electromagnetic pulse from a nuclear weapon – it is the arch-typical boat anchor – weighing 22 kg (about 50lb).

Temperature Control

Temperature control is via two fans designed to flush heat from the set by forcing air past a heat exchanger, from front to back – at a speed dependent on the internal temperature.

When the set is warm, the fans will idle reasonably quietly, but when the temperature rises the temperature control kicks in and ramps up the air flow. The mode switch allows the fans to be switched off.  They are a dead give-away in a tactical environment. The set will cut out if it overheats etc. While the noise of the set was a tolerable feature in military operations it is less attractive in an amateur radio shack because it sounds like a passing jet. A good technical description of the set can be found here.

In this article, Leighton Davies, GW3FSP creates a different user experience making the rig more acceptable in amateur use.

Having had one fan on my 353 decide to die very noisily I decided to replace the 3 phase fan with a 24 volt DC fan, (despite the availability of spare 3 phase fans).  The problem then was to find some way of fitting the new fan in the rear of the 353.  I decided to rip out the internals of one of the original fans and fit the DC fan inside its housing.

Removing the Original Fan


The fan is held in with 4 screws, these were removed and the fan removed.

Fan Removed

Tidying Up

I then cut and sleeved the original 3 phase wiring.








Making room for the 24V Fan

I then stripped out the internal motor, bearings, and fan assembly leaving a bare shell.

Fitting the Fan

Then came the hard bit, cutting out the internal casing to take the new square fan, this took some time(!) and after several hours I managed to fit the fan in the casing using hot glue to secure it in place – blowing outwards.

24V Fan Fitted – Inside View
Outside View 


I then fitted the fan assembly back in its original position with the 4 screws and ran the extended fan wiring along the spine of the 353 to the rear of the hour meter.  I used hot glue to stick the wiring in place out of the way of the outer case and other wiring.

The photo below shows the power supply wiring for the 24v Fan soldered to rear of hour meter.


You could of course replace both fans but then the fan noise might be distracting, with just one fan replaced I find the noise quite acceptable.

After testing the fan I replaced the set into its case and bench tested it to prove it working.  Job Done!

What I might do now this mod works is to look for the same size fan but one which has a higher speed and throughput to replace the other fan, this would hopefully keep the set cool and reduce the noise.

Editors Note:

All modifications published on this site are published for the purpose of experimentation. They should be carried out by a competent and engineer and at the risk of the owner of the set being modified.

A VRC 321 Side Step Modification (Removing the +2Khz Frequency Offset) by Leigton Davies, GW3FSP


In military service the clansman HF sets used an offset of +2khz while in USB, CW (W) and CW(N). mode.  In AM the dial frequency is the carrier frequency.

The purpose of this modification is to remove the 2Khz frequency shift when using SSB and the CW ( W ) and CW ( N ) modes.  This has the advantage of the operator being able to see the same frequency on the 321 as QSO partners using an amateur rig.

This article has been revised to correct wire colour errors for the CW mode select diode placement. revised 12th Jan. 2014.


I am assuming that the LSB modification is the same as I have previously posted, if not you will have to provide a suitable switch to operate this modification.

Going in…

Photo 1

Firstly you remove the set from the case , remove the 4 set screws holding the front panel in place and open up the front panel, looking at the rear of the front panel on the left hand side of the PA module is the Miscellaneous function PCB.

The mode switch wiring is routed to this in order to operate the mode settings.

In photo 1 above you see the DPDT switch I fitted to operate the LSB board, one section of the switch is unused, this section will be used to switch the side step on and off, connect 2 wires to the NORMALLY CLOSED contacts of the switch, feed the wires between the PA module and the front panel and pull the ends through to the side of the Misc function PCB where the loom wires connect to the PCB.

 Function Switch Connections

According to the circuit details in the EMER the function switch connects to the following terminals on the PCB:

  • AM – Pin 16.
  • SSB – pin 19
  • CW (N) and (W) – pin 20.

The CW mode switch positions are linked together at the switch.

However the numbering of these pins is ambiguous, so I removed the PA module and chased the wires from the mode switch to the PCB while noting the wire colour codes which are:

  • AM – White with Red trace.
  • SSB – Red with Black trace.
  • CW modes – Green with Brown trace.


Photo 2

Photo 2 – This shows the 2 diodes connected to the SSB and CW mode wire terminals, the negative end of the diodes connected to the PCB. I cut the wires to about ¼ inch from the body of the diodes, one diode to the Red/Black wire the other to the Green/Brown wire,  then twist the unsoldered diode wires together tightly and cut off about ½ inch from the diodes, solder them together.

Photo 3

Photo 3, right, shows the 2 diodes connected ( the black band of the diode to the switch wire ) to one wire from the switch, the other wire from the switch is connected to the White/Red wire for the AM mode.




Photo 4

Photo 4, Left, shows the completed wiring with sleeving pushed over the diodes.

Closing Up

Position the diodes and wiring to make sure they are not trapped when you close the front panel, replace the 4 set screws and tighten. 


Testing the Set

Tune to a convenient frequency on AM, monitor your transmission on a separate set switched to AM on the same frequency, you should be spot on frequency, switch both sets to USB. You should not need to adjust tuning on either set to hear your transmission, switch the 321 to CW (W)  and press the pressel, you should hear a 2Khz tone ( this is the 2Khz tone used to generate the CW signal ) switch the 321 to CW(N) and repeat the test, again you should hear the 2Khz tone.( The 321 uses USB for CW modes ). Set the 321 to SSB and switch to LSB ( if fitted ) and LSB on the monitor set,  when transmitting on the 321 you should be about 1Khz off frequency as the LSB mod needs to be 1Khz off frequency, tune the monitor set to resolve the signal.

As a further test, tune the 321 on SSB ( USB ) to a known transmission ( I used Shannon Volmet on 5.505Mhz )  you should hear a clear transmission, now switch to CW ( W )  you should still hear a clear transmission without needing to retune.

Mod done, box up the set and relax!.

Leighton. GW3FSP.


Replacing Expired Dial Lamps with LEDs in the VRC 353

A 2 Part Article By Leighton Davies GW3FSP

PART 1 – Replacing the dial lamps in a VRC 353 VHF Transceiver with LEDs

Revised 28th Feb. 2014

After thinking about the chances of finding genuine replacement parts for the dial lamps I decided to modify the VRC 353 with the modern equivalent.  This is a short description of what I did to replace the dial lamps with LED’s.

In this part the repair was carried out on a spare dial unit. In the second part the dial unit removal and replacement is discussed and I take the opportunity to turn off the 150Hz Tone.


The LED’s used to replace the dial lamps are standard White 3MM 4v @ 20Ma maximum rating. I got them from CPC P/No – SC11538.

After experimenting with 4 led’s in series I decided on a 2.2k series resistor giving me a current of 6 Ma , this gave more than enough brightness to illuminate the dial unit, ( having now fitted the modified unit I would however suggest a slightly higher resistance, say 2.8k. or even higher )

Lamp Holder

The lamp holder is a plastic fitting secured to the top of the dial unit with 2 screws which also secure the cable ties for the switch loom, there are 2 wires connected to the lamp holder, one is white with a brown trace connected to the left hand terminal ( positive ), the other is yellow with a brown trace ( negative) , the yellow/brown wire is connected to the right hand terminal of the lamp holder.

Top View Dial Unit

Top View Dial Unit

BEFORE you disconnect the wires check the polarity of the supply ! and note which wire going to the lamp holder is positive, then switch off and disconnect the supply !.

Disconnect both wires from the lamp holder, unscrew both screws and lift out the lamp holder, you will find the positive is to the left of the holder, you will need to extend this wire, I used a length of thin red flexible wire., sleeve the joint.



Lamp holder removed


The flat edge of the lamp holder is towards the front of the chassis.

Unsolder and remove all 4 lamps, be carefull the plastic will melt very quickly.

I removed the 2 wires .

The leds I tested with my diode check meter to make sure I connected them correctly, with the led conducting the positive ends go to the resistor end of the lamp holder, I then fitted all 4 leds with the round end of the leds showing about 1/8th inch below the plastic.

I bent the led leads about 1/4 inch from the base of the led at 90 deg, more or less making a ‘ T ‘ shape , I cut the leads about 3/8 th inch from the bend, made a small loop in the ends of the leads and fitted them over the terminal posts, I started from the left hand end of the lamp holder.

Then soldered the left hand connection, fitted the next led, soldered the joining connection, and continued ’till I had all 4 leds soldered but leaving the right hand connection of the last led un-connected with the positive lead sticking straight up, I then cut the lead about 1/4 inch from the base of the led leaving that lead sticking up, I then looped the wires of the 2.2K resistor as close to the resistor as possible, trimmed the leads and fitted the resistor over the led lead and the connector post and soldered the resistor in place.

Side View Lamp Holder

Side View – Lamp Holder

I then connected a 24v supply, positive to the outer end of the resistor, negative to the end led, it worked !. the current was just over 6.5Ma with more than enough brightness to illuminate the scale when fitted to my spare dial unit.

I now replaced the lamp holder, connect the negative to the left hand led post, the extended positive wire to the outer end of the resistor.

Top view of Lamp Holder showing Wiring

Top view of Lamp Holder showing Wiring








I have taken 4 photo’s of the dial unit and lamp holder, hopefully they will be good quality, I used my ‘new’ Samsung galaxy 7 gizmo.

Turning off the 150Hz Tone

As an extra little job, while I had the set out of the case I turned the 150Hz tone off, this is done by the 10 turn pot marked ‘T’ on the PCB retainer fitted on the left hand side of the set just below the TX turret assembly, there are 3 pots, the ‘T’ pot controls the 150Hz tone, The ‘D’ pot controls the data level and the ‘A’ pot controls the mic audio to the modulator card.

If the retainer plate is missing, the 3 pots are below the red warning sign, the ‘T’ pot is towards the front of the set, the middle pot is the data ‘D’ and the rearmost pot is the ‘A’ pot for audio.

Now back to replacing the lamp holder in the 353 VHF set….


On the terminal strip to the left of the synth module, the lamp holder wires go to tags 18 and 25.  The white with brown trace on tag 18, the yellow with brown trace on tag 25.

The positive supply is on the left of the lamp holder this needs to be extended to the resistor on the right of the lamp holder.  On my set the positive supply goes to tag 18, I measured full supply voltage.

One for the Pot

When I dismantle anything I use plastic tubs ( usually the tops from spray cans ) to keep the bits in, I suggest you do the same.

The Start...

The Start…

To start, the tag strip pcb is held with 3 screws, and one screw to the top pillar from the module to the right of the mode switch, remove the 3 screws and washers, also the 1 screw from the stud, put in a tub.

Tag Strip Removal

Tag Strip Removal



Remove the two studs from the left of the module and the one screw top right of the module, tub them.



Knob removed

Remove the mode switch knob ( set it at narrow first ) 3 screws, careful, the coupling will now fall out!  Put these bits in a tub, you now have to remove the round ‘nut’ holding the switch in,

( I used a blunt 3/4 inch wood chisel as a screwdriver) put the ‘nut’ and washer in the knob tub.

Tag Strip and Switch

Tag Strip and Switch


To remove the lamp holder the 2 screws holding it to the top of the dial unit must now be removed.  Unfortunately the left hand screw is under the chassis fitting for the tag strip removed earlier.  The 4 screws holding the dial unit must be removed to allow access to this screw, there is a sealing gasket fitted in a machined groove in the dial unit, be careful not to damage it.  Put the 4 screws and washers in a tub.

VERY gently, pull the module up and to the right, it will sit on the top of the chassis, move the tag strip left and then push the mode switch through the hole and to the left.

All 3 Detached

All 3 Detached

You will now have access to the lamp holder, there are several ties holding the loom together, these must be untied/cut and removed.

The dial unit will move just enough to allow removal of the 2 screws, do not lose them in the set! You will need to remove the cable clip on the left of the lamp holder, there may be other ties you may have to remove, GENTLY tease the wires up and over the top of the dial unit switches so you can see the whole of the lamp holder.

Dial Unit Moved

Dial Unit Moved

Slide the lamp holder to the left, you can now unsolder and remove the 2 wires to the lamp supply, remember to extend the positive wire!. the negative can be connected to the left hand led post.

Lamp Holder Ready to Remove

Lamp Holder Ready to Remove

( This is when I went for a coffee break ! )

After replacing the lamp holder and re-soldering the wires – the 2 screws ( with cable straps ) can be refitted.

Tease the wiring to the switches back into position gently! If you want to fit cable ties now is the time, you will need the smallest you can find.


Refit the 4 screws holding the dial unit to the front panel, make sure no wires are trapped.

Refit the module removed earlier, one screw and the two studs, short stud at the top.

Refit the mode switch, washer then the nut with the knob retaining ring, the large hole in the ring to the left.  There is a lug on the knob which fits in there, the coupling goes in next, ( try a spot of grease to hold it in place).  The slot in the mode switch needs to be horizontal ( narrow mode ) then fit the knob and tighten the 3 screws.

Next refit the tag strip, 3 screws for the pcb and one for the stud fixing.

The End

The End

(This is when I went for a break, 2 large coffee’s and a lump of fruit cake ! Yummy )

Powered up the set and – it worked!



This whole exercise took me 4 hours, including taking the photos with the Galaxy 7 and making various notes to get the photo’s in the right order, the modification to the lamp holder took about an hour including testing.

Have fun.

Leighton, GW3FSP


Curing the RT 321 Sticky Coil Drive Mechanism with a Selector Unit Coil Assembly Replacement

In this article Leighton Davies, GW3FSP discusses the ultimate option for the repair of a sticky coil drive mechanism in the UK\RT 321.




I decided to carry out this repair in order to re-furbish the Selector Unit due to tuning problems caused by the coil drive mechanism in the set sticking and giving the characteristic continuous un-ready bleeps (often ‘cured’ by a sharp tap with a blunt object in the right place!).

There are several levels of repair and this one can be carried out if my ‘fix’ of lubricating the bearings, gears and coil tuning guides and screw drive does not cure the problem.

Testing the Replacement Unit

Before Stripping

Before Stripping

This can be achieved before replacing the coil pack by applying 12 volts across the motor terminals to drive the slugs in and out of the coils to check operation.  Also VERY lightly oil the sliding guides, the gears, bearings and the screw drive system.

Out with the old….

Dismantled Unit

Dismantled Unit

Removing the Selector unit as before (2 screws top and bottom, unplug the 4 coax leads, unsolder the link wires under the coax leads, and unsolder the tag strip connections to the PSU – (Or remove the PSU and tag strip from the chassis and move them to one side).



Another View of the Dismantled Unit

Another View of the Dismantled Unit








Remove the outer case completely from the internals and removed the small PCB with the relays fixed to the unit.

Connections to the Coil Assembly

Link Wire

Link Wire

Removing Wires.  The coil assembly is connected by very few wires;  2 to the motor ( note the + and – connections), 4 to the coils themselves (note which wire goes where) and 2 wires to the limit switches, one by the motor, the other via a feed-though terminal to the PCB.  When this link wire is removed from the coil pack, fit it to the new coil pack ( see photo).


In with the new…

New Coil Pack

New Coil Pack

Refitting.  Refit the coil wires, motor wires, switch wires and the small PCB with the relays, and the main PCB to the Coil Assembly.  GENTLY refit the Ledex Drive and Coil Assembly into the bottom case.  Be careful with the 4 wires to the coils, tweak them gently into position.



Screw the Coil Assembly and Ledex Unit back into the case.

Coil Pack Installed

Coil Pack Installed

Check all wires you removed have been replaced where they should be and have not come adrift as they are all single core and quite fragile.

Refit the top case and check all screws are tight.




Optional Test Rig

Test Rig

Test Rig

This bit is optional – I made up an extension cable using some flat ribbon cable from an old floppy drive cable from a scrap PC, there are 12 wires from the Selector unit to the tag strip, see photo, I then connected the selector unit to the tag strip using the ribbon, plugged in the 4 coax connectors, I used a mouse mat to insulate the selector unit from the chassis and checked everything.


I then powered up the set and checked that the Mhz tuning operated the Ledex and the Coil Assembly from 1.5 to 29.5 Mhz in 1 Mhz steps, it worked ! – end of optional test.


Refit the selector unit in the chassis, re-make the 12 way tag strip wires, plug in the 4 coax cables and re-fit the PSU.

Check the 12 wires AGAIN to make sure they are in the correct sequence.

Switch on and test the full Mhz tuning range 1.5 to 29.5 Mhz in 1 Mhz steps (slowly !).

When I carried out this repair I was happy to say everything worked.

General notes:

Hopefully if I need to repeat this with the other set that will be somewhat easier than this set, it took me several days to complete, as I had problems with a dirty Mhz switch which was not sending the correct signals to the Ledex De-coder to tune correctly.  This took a day to sort out by itself.

Leighton.  GW3FSP

An implementation of The Lower Sideband Modification to the UK\RT 321

By Leighton Davies – GW3FSP – July 2013

The mod kits for this job were obtained from Oliver Tillet G3TPJ, they are a small double sided PCB with pins for connection to the 321 set wiring, included is an instruction sheet with diagrams of the various works which are required and wiring instructions, these were read very carefully referring to the internals of the 321 in order to make very sure I would know exactly where and what I needed to do.

321 LSB Mod PCB

Switch Mod

The first problem anybody faces when doing this mod is how to provide an LSB switch. I decided to use the Elapsed Time Indicator (ETI) socket which has long been a dormant feature of the 321.

To achieve this I ran in the extra wiring required, the 2 red supply wires from where I was going to put my switch in place of the fuse holder originally for the elapsed time capsule which I removed after snipping the wires and insulating them, you may also have 2 small capacitors to remove, one across the ‘fuse holder’ one from the fuse holder to ground.


Lower Socket in location…

Wiring up

I then fed the red supply wire to the PCB location using the loom as a guide feeding the wire through the lacing cord leaving about 6 ” or so spare at the PCB end.

Complete PCB Showing Wiring

I then removed the wire from tag 14 of the tag strip, soldered on a length of white wire and sleeved the join, an extra white wire then from tag 14 to the PCB location again leaving an extra 6″ or so.

Siting the PCB

The lacing needs to be cut from the loom where the PCB is going to be fitted , I marked the coax from SK1 where I was going to cut it where the cable clip is.


Bracket and Clip…

…removed and ready to take PCB

Making Space

I then removed the cable clip and bracket, 1 screw for the cable clip and one for the bracket from the side of the chassis, and the nut and washers holding the bracket to the main chassis, once the bracket was removed I decided to put 1 washer and the nut back onto the screw and tighten down, I then snapped off the rest of the screw with pliers, I decided I did not want the rest of the screw moving about if I just snapped it off where it was.

I then removed the coax cable from SK1 to the next module from the set, cut the coax where I marked it , trimmed the sleeve back and connected the inner and outer to the required pins on the PCB.

Connected the 2 white wires to the required pins and then a red wire I had used for the 24v supply to the pin on the PCB, trimming the length of these wires to leave about 2″ of slack, I did not connect the ground wire as the coax outer braid does that and I’m suspicious of earth loops. I then checked all the wiring I’d done to make sure I had the correct wire going to the correct pin on the PCB and trimmed the pins back as far as I could.

Fitting the Board

I then used a small component bag opened out to completely wrap the PCB, this was then taped in place with ordinary insulating tape, I fed the PCB under the loom, secured it in place with a cable tie, re-fitted the coaxial cable and also fitted several ties to secure the loom where I’d removed the lacing cord.


That Switch…

Lower socket out...

Lower socket out…

On the original modification I fitted the switch straight into the hole using a thin washer inside the panel and another washer on the outside as the hole is about 1/8″ larger then the switch barrel, however I then tried the following method on the second set as an experiment and as it worked I then re-worked the first set to copy this switch fitting method.

I then placed the set so I could get at the back of the front panel with the panel flat on the bench, moving the wires gently out of the way I then stuck a small square of masking tape over the hole (about 1″ sq )

And pushed it firmly into place making sure the tape was flat and not pushed into the hole, I used a wad of tissue paper folded over repeatedly and pushed that on top of the masking tape, with the front panel closed this will push against the tape stopping the tape falling away from the panel.

Closing the front panel I then put the set on it’s end with the front panel uppermost.

I then mixed the Araldite I was going to use to fill the hole, I used just a bit more hardener than adhesive, mixed it well and poured it gently into the hole filling the hole very slightly proud of the panel.

Then left it to set over-night.

The base for the switch ready…

And believe it or not it had! (does what it says on the tin(ed)).  I opened up the front panel and removed the tissue paper and masking tape from inside the panel, grabbing my battery powered BnQ drill and put a small pilot hole through the centre of the filled hole first ( 3mm drill) VERY GENTLY !, then a 6mm, then 8mm finally the 12 mm.

The switch I decided to use was from Maplin Electronics and is a sealed IP67 spec switch, ( N25KA ) and I also fitted a switch cover ( YL01) which is a water/dust proof cover, done up tightly.

l Switch front

LSB Toggle Switch

 Final Wiring

The red supply wire to the PCB was then connected as was the feed to the switch, I took the supply from the tag strip sticking out of the metal screening can over the rear of the 2 audio sockets on the front panel, One tag strip has the 2 audio screened leads, the other has the PTT and audio out wiring, the 3rd connection from the bottom of the panel (the hinged end ) has 24 volts on it ( check to make sure ! ) the other red lead feeding the switch was attached there.

Running Up

I then closed and secured the front panel with one of the top bolts.  Connected power, headset, Turf unit and dummy load and switched on (fingers crossed), no bang !.  I dialled up on 20 metres – I think I used 14.202 Mhz , and tuned up, set to low power then set my 847 to 14.200 and tried USB to and from the 847, yes it worked, switched to LSB on both and dialled up 14.198 on the 321 and it worked.

Later that evening I tested this set with a neighbour Amateur and all worked ok on AM, USB and LSB.

The modification was then repeated on the other set with the same procedure and all ok.


The photo’s were captured using an old web-cam which has proved far more usable to produce small but quite good quality pictures, these I have up-loaded to the 321 Yahoo Group site for your perusal.

(Editors note: I hear the iphone has become almost the defacto standard for photographers due to its image quality and portability.  These shots are not too bad and convey the meaning.)

Have fun guys!


Technical Diary – Servicing and Commissioning 2 New Second User 321’s

By Leighton Davies GW3FSP


Leighton picked up two very reasonable VRC321’s and the Test Kit condition.  What follows is his diary leading up to commisioning the sets.  At the price he paid a working set would have been a miracle and both had minor faults.  The most common fault being the sticky Ledex which up until now outside of GCHQ the servicing of this has only ever been described as a violent tap on the case at the appropriate time.  Leighton demonstrated a more practical approach to bringing such a radio into service in an enjoyable series of posts on the 321 Yahoo Group.  The edited version follows with thanks to the contributions of Iain, G0OZS, Jim and others who contributed.  The posts are reproduced here by kind permission.

Stu – G4IYK


Selector Unit Side View – Coil Tuning Unit


20 May 2013 16:16 Subject: [321] 321 Group New member
Hi guys, thought I would introduce myself.
Been licensed since 1976, mostly on vhf/uhf, since getting my late father’s
call I’ve been a bit more active on the hf bands, started to collect
military sets last year when I bought two old WS 62’s and have been
re-furbing them, and , an old R 209Mk2 receiver.
My military experience in REME was limited to the WW2 kit up to the
introduction of the ‘A’ , ‘B’ and ‘C’ series sets, ie, the 18, 19, 62 sets
etc, with very little experience of the ‘new’ kit coming in then.  Just bought two UK/RT 321 sets and the ‘Conditioning Kits’ for them.Slowly getting the kit needed together to run up these two 321’s, so far I’ve got the TURF unit, headset with presell and the ‘C’ connectors and made up a set of various patch leads. All I’m waiting for now is the power lead, not having met these sets before any advice on starting up these sets would be very useful, I as yet have no manuals or ‘crib sheets’ on these sets, they were somewhat dusty when they were delivered having been stored by the previous owner who had not run them up having no time to get the bits for them.I have also joined the Clansmanuser.org site and submitted a post, still waiting for a reply there.Any help greatly received. Leighton. GW3FSP.
22 May 2013 00:51
Subject:    [321] Power supplies for the 321 etc
I’ve been trolling through the earlier posts on this group, and there are a few posts regarding what psu’s to use.
I have here a Collins 618T ( ex Concorde ) hf transceiver which did have a 3phase 400hz 115volt psu for the 1500v ht for the PA.I fitted the 28v dc inverter supply as obviously no 3 phase supply available, to run the set I use a 28volt aircraft battery floated with a 28v 42 amp switch mode power supply. The inverter psu takes 32 amps at full power ( 400 watts from the transmitter ) this will be the supply I will be using from home, the switch mode supply is adjustable from 20 to 30 volts so if needed I can reduce the supply to 24 volts, it depends on what the EMER’s state is the prefered supply voltege, unless somebody here can tell me ?.Also, I use on hf a Yeasu FL2100z Linear, at the moment I normally use it with either the Kenwood 530s or Yeasu 847 transceivers, I will be checking what input this needs for a decent output from say 100 up to 300 watts and then see what attenuator I need to make up for the 321.
Leighton. GW3FSP.
22 May 2013, at 15:45 Iain Moffat <iain@…> wrote:
> Leighton
> The Clansman 50A PSU used with the 321/322 set was 28v out – in truth the inverter in the 321 was happy with anything 22 to 32 volts – when running on batteries weirdness began at 22v or below (not that I should ever have let that happen!)
Hi Iain, you mention an inverter inside the ‘321, I thought these sets were all solid state including the P/A ?.
Do these have a valve P/A ?
> Leighton. GW3FSP.
22 May 2013 20:33
Subject: Re: [321] Re: Power supplies for the 321 etc
I may be slightly incorrect but I tend to call any DC-AC-DC PSU an inverter!
The 321 is all solid state unless you count the LEDEX preselector as electro mechanical. But the PSU is an isolated switch mode unit so essentially an inverter with 20-32v in and various stabilised voltages out – without the EMER I can’t remember them all but certainly 3, 5, 6 and 12v – I think the PA runs from something higher. The separate 250W PA for the 321 is based on valves with a transistor HT PSU.
The 353 VHF set really is hybrid and has valve PA and front end with 800v HT, and motorised turret and coarse tuning. The RT320 HF manpack although all solid state needs 110v for varicaps which comes from a non isolated switch mode PSU.
73 de G0OZS


22 May 2013 21:25 Subject:    RE: [321] Re: Power supplies for the 321 etc
Now back at my desk I checked the EMER H592 pt 1 page 80 para 225 and block diagram following. The 321 PSU is fully isolated (so the + and – inputs are independent of ground and the set can be safely used in positive earth vehicles). The input is regulated to 15-17V and chopped to drive the transformer. There is a feedback loop to maintain a constant output from the chopper stage although the output is increased in high power TX mode. The chopper & transformer is actually described as an inverter in some paragraphs of the EMER and the block diagram. The transformer output at 28V (RX or low power TX) or 33V (in high power TX) is rectified and regulated in independent supplies giving
+33V or +28V depends on TX/RX – non critical supplies
+30V or +25V depends on TX/RX – PA supply
Most outputs are series regulated but the main +12V is switch mode for efficiency reasons
The chopper is synchronised to a synthesiser output at around 25KHz but will free run at 23KHz if synchronisation fails (useful for diagnostics ?)
The mean ALC uses the PSU to measure the PA current and sends an ALC control voltage to reduce PA gain as the current reaches 3A. The PSU will trip under the following circumstances
1. Short circuit of any output
2. PA current exceeds 3A despite the best efforts of the ALC

3. Output voltage high due to regulator failure

4. DC input below 20V or above 40V



73 de G0OZS


24 May 2013 12:11 Subject:    [321] UK/RT 321
Yea !, the power lead has arrived !.
I have a little shopping to do shortly then I’ll be taking a good hard look at both these sets before I decide to power them up one at a time and see if I’ve got 2 good sets.
Leighton. GW3FSP.
24 May 2013 18:12 Subject:    [321] UK/RT 321 sets
I appear to have 2 working sets !, both receive and transmit on AM, CW and SSB, the tuner works ok but I notice the Match control makes a definate ‘scratchy’ noise when turning it but it tunes ok thats the main thing.
Also when hitting TX on ssb there’s a burst of noise on my FT847 before speech clears and is of quite good quality considering I’m using a very second hand headset assy, One set I’m testing on AM outputs about 5 watts on low power and 25 watts on high power, I though AM was limited to 7.5 watts ?.
I wish my VMARS membership would come through, I really need to get hold of some documentation for these sets.
Right, back to play !.
Leighton. GW3FSP
25 May 2013 20:52 Subject:    [321] 321 sets
I spoke too soon !, been testing these two 321’s I have here, one of them on AM low power showed 5 watts, high power showed 25 watts, Then I checked CW low and high, then SSB low and high, the latter sets of figures were correct, left the set on whilst I re-filled my cofee, tried transmitting and I had about 1/2 watt out on CW, low power or high power, I think one of these sets has the P/A problem I’ve heard about where the ALC transistors protecting the P/A devices fail, am I right ?.
The other set performs as per spec, 5 watts low power all 3 modes and only high power on SSB and CW with AM at just over 5 watts.
I will however have to open up the TURF unit, the match control makes a definate scratching noise on the rx when it’s turned, why not known as it’s only supposed to adjust a pair of capacitors and a switch, hmmm.
Leighton. GW3FSP


26 May 2013 22:01 Subject:    [321] Clansman 321 Kit
Apparantly I’ve been suffering from finger trouble with these 321’s, found some instructions on tuning them up and set up what I’ve called the ‘good’ set, followed the tuning instructions to the letter and – looks as though I now have full power on AM,SSB and CW, the AM is now hitting just about 30watts on high and 5.5 on low, I’m wondering if it’s my finger trouble which caused the other set to shut down the P/A altogether , I shall see tomorrow when I put that one back on the bench.
20m been quite lively on the 321, listened to some ‘W’s chatting for quite a while no sign of any drift at all.
Leighton. GW3FSP.
27 May 2013 13:50 Subject:    [321] Clansman 321 Kit
Just had my ‘suspect’ 321 on the bench, and it’s definately suffering, the rx is quite deaf, listening on 14.070 to the PSK transmissions on my 530S signals are loud about S 9 + a bit, the 321 is picking them up but the ‘S’ meter is barely registering, also on tune, the meter is immediately all but full scale but I can peak the TURF, when I try low power CW into a 50 ohm dummy load I get 5 watts then power reduces to zero in about 3 seconds, Full power gives the same result, I get about 6 watts, so this one needs a lot of TLC, my VMARS membership should be ok from the end of this month so I can start downloading the manuals ready for the grand opening ceremony !.
I can hear the various motors churning away inside when I change frequency but not knowing what I’m going to be looking for I’m not opening this set untill I get the manuals and spend a few hours reading up on the internal systems.
Any hints of course will be very greatfully received !, Hopefully the fault will be common to the rx and tx systems, it’s on frequency, so I’m going to see what these motor driven systems are before thinking of anything else, One thing I have found is the BF115’s which I believe are fitted to the PA transistors as heat detectors, bought 10 of them, just in case!.
Might be a power supply problem but as far as I know these sets go into ‘bleep’ mode if it detects a psu problem, which I don’t get.
Back to the ‘209, it’s time for another delve into it’s innards.
Leighton. GW3FSP.

Selector Unit Top View Showing Coil Drive Motor

29 May 2013 17:39 Subject:    [321] Clansman Kit
Decided to bite the bullet and open up the dud 321, following some info I received I removed the case with little trouble, One job I needed to do was to replace one of the little terminals on the bottom right of the front panel, did this ok no problems.
I then perused the internals, couldn’t find anything visibly wrong, so I then unplugged and replugged all the little coax connectors checking inside the plug and socket with a magnifier, nothing wrong there.
Wiggled all the soldered connections looking for dry joints, nope !.
Plugged in the headset, Turf unit, power and switched on, it worked !.
Tuned up the Turf on CW low power using the tune switch, I had low power CW and AM, also high power CW and AM, also the rx was on par with my 530S on 14.070 listening to PSK signals, and SSB was ok rx and tx.
Coffee time !, got back to the shack the set was bleeping !, then cleared and working ok, about 1/2 to 1 hour later noticed the carrier I was listening to started to rapidly shift up and down then normal, later the rx went quiet and the S meter went down, bleeping again, then cleared and normal, this frequency warble happens ittermittently with the occasional bleeping then everything comes back, Once when I switched the set off for a few minutes then on again the bleeping continued and I heard nothing from the tuning system untill I rapped a module marked No7 Ist and 3rd Local oscillator then the set tuned and burst back into life.
Further delving needed here, I think I’ll re-make all the solder joints on this module’s connections to the chassis. Unless you know better !.
Leighton. GW3FSP.
29 May 2013 22:56 Subject:    [321] Clansman 321
Been delving into the innards of this set, not simple!, however, I’ve re-soldered all the connections to the Local Oscillator module, could not find anything really, so I’ve now had this set tuned to 14.070 for the past 3 hours and it’s sneezed a couple of times but for the last 2 hours hasn’t done so much as a hiccup!.
I’m going to order up some BC107 spares , take the module out, open it up, connect it back up and do my freezer spray fault finding trick, might work (oops it just sneezed again) going to be the only way I think to find why this module is playing up, as it’s out of the case (a damn great big heat sink) I’ve rigged up a little 12v fan blowing on the top heat transfer plate to keep it cool.
If anybody has any other ideas as to the fault I’m all ears !.
Leighton. GW3FSP.
30 May 2013 22:02 Subject:    [321] Clansman 321 Kit
My dud set has now been on 14.070 listening to PSK for about 5 hours, it sneezed 3 times for about 10 seconds each time, I’ve ordered some spare transistors for this set and when they arrive I’ll be busy trying to find out which ones are failing in the Local Osc unit 7.
One question however, when I replaced the line terminal on the front panel I found a little potentiometer on the panel, just alongside the BNC connector, seems to be behind a fitting on the front panel with an allen key screw in it, any idea what the pot is for??.
Leighton. GW3FSP.

31 May 2013 12:59
Subject:    [321] Clansman 321 Kit
Never rains but it pours !, another fault has started giving problems, the selector system is stalling when tuning the set, The Ledex works immediately, but the motorised selector system sometimes stalls and will not tune until I give the area underneath the set where the selector sits a decent whack using a screwdriver held in place and then whacked with pliers, the motor then runs and tuning is completed, I have to say the noise this motor and tuning system is making does not sound happy at all.
Ho hum !, here we go, screwdrivers, pliers, spanners, soldering irons and de-solder station at the ready, ( I’m glad the other set is ok ! ).
Leighton. GW3FSP
Friday, May 31, 2013 7:34 PM Subject: [321] Clansman 321 Kit
Set all back together, I removed the selector unit, opened it up checked around inside, put a tiny amount of lube on the motor, gears, and slider mechanism, put it back together, set still works, and this time when I switched on the selector unit motored away quite happily and a little quieter than it has been, and – I checked the frequency transmitted at 29.999 mhz on AM and found it was out by about +2 Khz, I adjusted the little trimmer through the fitting on the bottom right of the front panel, frequency is now hovering around +/- 10HZ close enough for me !.
Now ‘on soak’ tuned to 14.070 again so I can hear the PSK, waiting for it to either sneeze again or go phut !.
I’ll be posting 4 shots of the selector, I appologise now for the quality of the pictures I’m using a fixed focus Fuji digital camera I’ve had for many years.
Leighton. GW3FSP.

Selector Unit – Underside view

June 01, 2013 11:38 AM Subject: [321] Clansman 321 Kit
Hi Stuart, Thanks for the reply, I checked the frequency on AM mode deliberately, as you pointed out using SSB I have to tune +2Khz to resolve the ssb signal, I had quite a long qso last night with a fellow amateur about a mile away using the set on both ssb and am to make sure all ok, he set 14.160 I set 14.162 and he came through perfectly on ssb without my having to fine tune at all, AM required me to tune down 2khz as the filters in this set are extremely sharp !, after several hours I checked the AM frequency again and it was +10hz at 29.999mhz.
So far after my delve into the selector unit it works far better and the set tunes first time without application of the persuader!, I think the main problems were the lack of lube on the gears and sliders for the coil slugs, it’s still a bit noisey but nothing like what it was, if I can get another module I’ll give that one a good going over then swop them over, the motor is 28vdc so I should be able to rig up a little circuit to drive the motor back and forth to make sure the tuning slugs move easily and hopefully a lot quieter.
Leighton. GW3FSP.
01 June 2013 23:49
Subject:    [321] Clansman 321 Kit
Been using this 321 for most of the day on 20m, since cleaning up the selector unit and giving it a little lube job and some TLC the set now tunes up on whatever frequency I dial up, power is lower on the higher frequencies but at both these sets have a MFG date of 1980 I’m not really surprised, I’ll have do a search on possible equivalents for the drivers and P/A devices and see if they are usable, RX has really picked up now the selector’s working better and matches the 530s using the same antennae, It still gives the occasional sneeze (bleeps) but only for 3 or 4 seconds, still wondering why, the transistors for module 7 have arrived but at the moment I’m going to put the R 209 Mk2 I have back on the bench for a while, and I still have the two 62 sets to finish off. it’s fun being retired, never a moment’s peace!.
Leighton. GW3FSP.
03 June 2013 18:26 Subject:    [321] Clansman 321 Kit
Along with these two 321’s I also picked up 2 of these – Test Kit Condition, NSN – 6625-99-620-3592, As far as I can see from the instruction plate inside these are used to carry out field tests on the 321 to check their operational status, are there any further or more detailed instructions for using these contraptions anywhere?.
They look quite fascinating bits of kit with all sorts of cables and fittings to test various bits of the set and before delving any further and trying to use one of these kits I thought I’d better ask for help and advice from those who know a darn sight more than me !.
The set I’ve ‘repaired’ I’ve now re-cased and is sitting on the floor awaiting use as I’m now working on my R 209 mk2 receiver for a while.
Leighton. GW3FSP.


03 June 2013 20:31 Subject:    RE: [321] Clansman 321 Kit
The TKC is basically a power attenuator. It has a dummy load power meter for TX testing – the range is set by the radio selector based on expected output Power producing a ‘good’ reading. The path between working radio and RUT for RX testing is basically a 94dB
fixed attenuator plus a switched attenuator with the steps marked on the
large front panel rotary switches. To guard against TX to RX leakage the
input signal is mixed with a 200KHz oscillator and the mixer output is set by the radio selector (coarse) and the Adjust level (fine) controls. It can be used with a QRP rig like an FT817 (use 320 low power settings on HF or 351 settings on VHF) as quite a good signal generator for much less money than a real one capable of SSB ! One of these years I intend to produce calibration info for use with an FT817 and a meter scale overlay for power measurement in watts.RegardsIain
73 de G0OZS
05 June 2013 11:59 Subject:    [321] 321 driver and P/A transistors
Hi guys, has anybody got any up to date info on which alternatives are available for the driver transistors (VX6537A in my sets) and the P/A transistors (PT6748 in my sets) I’ve been snooping around various sites looking for possible replacements and I’m finding dozens but no link to the current devices, even my favourite site (datasheetarchive) has nothing on the 2 devices fitted which is rather strange as they have a very extensive archive on older devices.
There are loads of general purpose hf driver and P/A devices available for hf tranceivers out there but will they work in the 321 series?.
Leighton. GW3FSP.

09 June 2013 00:21 Subject:    [321] Clansman 321 Kit
My ‘repaired’ 321 set appears to be working well, it’s very stable once it’s ‘warmed up’ about 10 seconds after tuning, since I adjusted the frequency it’s still within 10hz, rx is very good and not all that noisy compared to my 530S and FT847, output however is low at the top end of the range but as this set has a MFG date of 1980 I’m not at all surprised, I’ve found several transistors which could be used as P/A replacements but it’s now deciding whether to get some of these alternatives and see what biasing differences exist and then try and fit them and see what happens.
Leighton. GW3FSP.
09 June 2013 07:48 Subject:    Re: [321] Clansman 321 Kit
I think all 321s show a significant power variation with frequency – I seem to remember the spec in the EMER is 2-6w low power and 25 to 40w high power – i would normally expect 30w on top band, 40 to 45w on 80 40 and 20 and 25 to 30w on 10 and 15m
73 de G0OZS
10 June 2013 22:45 Subject:    Re: [321] Re: Clansman 321 Kit
The manufacturer was MEL (Mullard Electronic Laboratories) in Crawley. It was already a Phillips subsidiary and I think has lost it’s separate identity since the 321 was built – I am not sure if it is still part of the Phillips group or even still in business
73 de G0OZS
Sent from my iPhone

Selector Unit Side View Showing Ledex Drive

11 June 2013 16:28 Subject:    [321] Clansman 321 Kit
The second 321 has now been given a little TLC on the selector unit, again removed the unit, covers off, removed 2 pcb’s and the panel with the 4 coax connectors, very lightly oiled the bearings, motor and the slug mechanism and screw drive, re-assembled the whole lot and tested the set from 29mhz down to 2mhz and very pleased with the results, tuning is quicker and quieter.
Checked the frequency at 29.9999mhz and it’s -12hz on AM. so I’m not adjusting the set for that size of error, the other, now TLC’d set is still within about +10hz. and so far having been soak tested for quite a few hours didn’t sneeze once, I can only assume the un-ready failures were due to the frequency error I corrected via the little adjuster through the front panel (I hope so!).
So far both these sets have proved fairly easy to open up and get into, I only hope I can keep them up and running without too many problems.
Leighton. GW3FSP.
13 June 2013 16:03
Subject:    [321] 321 Kit
Just sent off a request for several of the EMER’s for the 321 kit, at least I can then find out (more or less) how the internals of these sets work, and learn far more about the various modules and their workings, and find out if what I’ve done with the selector units was correct, too late anyway they’ve both been lightly lubed.
Both sets been run up from 80m to 10m with no further problems with the selector units which now go home and tune quietly and much quicker than they did before my TLC efforts.
For the time being this is all I can do with these sets so my postings will be rather sparse until I go through the manuals when I can download them and start asking more questions.
I hope my various missives have not been too onerous for those with far more in depth knowledge of these 321’s but I find the only way to learn about this new kit is to ask a lot of possibly mundane questions.

(On the contrary – please don’t stop 😉 (Ed.))

And now more coffee and back to the 62 sets.

Leighton. GW3FSP.