Clansman Manpacks for Amateur Use - Part 1

I noticed that there is a letter in the back pages of Radcom this month becrying the lack of information on the usability and conversion of Clansman radios for amateur use. Im not sure exactly where the correspondent has been looking, but there is plenty of info out there. But, I will make a brief recap here on my blog, to try and collate some usable data.

I will only deal with manpack, and not vehicle, equipment, as that is what I have experience of.

The Clansman Series

There are seven radios in the manpack Clansman series, but not all are usable for amateur purposes. These radios are -

PRC-319
PRC-320
PRC-349
PRC-350
PRC-351
PRC-316
PRC-344

I shall treat first with those that are NOT suitable for amateur use

PRC-349

The PRC-349 is the 'smallest' of the Clansman range. Intended for section level comms, it provides 250mW FM output between 37 and 47MHz in 25kHz steps. As such it does not cover any amateur band and cannot easily be made to do so. Despite this they are readily available. It also requires a 150Hz subtone to open its squelch, and unlike other FM radios in the range is not capable of internally generating this tone. Also, although it uses the standard Clansman audio accessories that are common to most of the series, its antenna is not usable on any other radio, and its 12v battery is also unique, a shame that it isnt usable on the amateur bands really, as I have several hundred of those batteries!.

PRC-344

The PRC-344 is a UHF AM radio intended for Forward Air Control. Capable of operating throughout the UHF military airband, and able to provide a homing beacon transmission. For very obvious reasons this is of no amateur use whatsoever. It does however use the same 24v batteries as the PRC-320 and PRC351. But thats all it has going for it. Oh, and its flexible discone antenna, commonly known as the 'Bob Marley'!

SO with those two unsuitable radios out of the way, lets look at a couple of the rarer units

PRC-316 (A16)

I dont have any experience myself of the A16. As can be seen by the designation, it is not really a Clansman radio, rather a late entry Larkspur unit, intended for long range patrol use. It operates on a number of crystal controlled frequencies and features a rather groovey built in Morse key! Can be pressed to amateur service but the cost of crystals on top of the cost of such a rare set is probably prohibitive. Still, a nice unit for a collector.

PRC-319

Another set I have no personal experience with. The 319 is capable of CW and SSB comms throughout the HF spectrum, at I believe a respectable 50W, and with a built in auto-ATU. It is audio and battery compatible with the 320 and 351 radios. A big drawback for amateur use is that it operates on 10 direct entry frequencies, with no provision to 'tune around'. Its main military use was for sending 'burst' data - encrypted digital messages sent at a high rate to evade enemy RDF. Usable at a push for amateur radio, but fetch very high prices.

This leaves us with the PRC-320, PRC-351 and PRC-350, which are the radios that are most suitable for amateur use. I will treat of these radios in my next post.

CHOTA this year?

Ive just compiled and sent an email to the office at Selby Abbey, to ask if they would consider hosting me for this years Churches On The Air day, on the 10th of September.  Two years ago, myself an Mike operated GB0SML from St. Mary's, Lead, near Saxton (commonly known just as Lead Church), which was a logistical nightmare due to its remoteness from any utilities (not even a cell signal!) and also a Scheduled Ancient Monument! Selby Abbey on the other hand, is fully geared up for visitors, has electrical power, water, sanitation and heating, plenty of space to operate, grounds and possibly its tower for antennas, and an endless source of refreshment from its tea room! It would be the ideal station, and a very prestigious one!

Ive also received the SG8002CA-PTB oscillator that will form the heart of the LSB conversion module for my 'test-bed' PRC-320. This is a tiny surface mounting rectangle of technology! ITs packed safely away until im ready to build!

The 2nd Chinese Pixie kit also came today. I plan on building that in a custom aluminium sheet 'cube' with a PP3 battery box below, and a built in Morse key!

But before any of that - ive to clean the workshop! Julie has threatened to tidy up for me if I dont do it, and that would almost certainly mean losing some critical component! Besides, ive to clear space for several hundred PRC-349 batteries!

PRC-350 fixed (hopefully)

I finally found a few moments to test the -350 on the bench with the case open, too see if I could find what was causing the modulation to cut out. With the radio connected to the Marconi 2955 via its mini-BNC connector, I found that the 150Hz tone was waaaay too high (some 2.5kHz!) and the mic level too low. Some tweeking put the tone modulation back to a sensible 1.5kHz (for use with the PRC-349s) and turned up the mic audio so that my typical voice level reached an average 3-4kHz max deviation. This was all done as a 'rough' guess, as the Clansman sets, despite having agressive VOGAD action, it seems do not have a limiter, so unlike the Kenwoods I used to service, I couldnt see the audio distorting at higher deviations. I suppose if i'd bothered to connect up the audio to the 2955 to provide a known steady level tone, I could have made a more accurate job of it.

Perhaps more importantly for this set, it occurred to me that the bad modulation was noted on an air test when using whip antennas. With the radio open on the bench, a quite startling discovery was made

The battle antenna connector was not connected! The wire, which is the pink one you can just see in the top left of the lower half of the radio above, had broken right at the PCB.

After quite a tricky job to remove the remains of the broken wire from the solder pad, which is not only in a difficult corner and further blocked by the flexi-PCBs and coax, but also under a shielding plate, I resoldered the wire and reconnected the battle antenna connection. All tested well on the Marconi, and a further test on air between the -350 in use by Sam and a -349 down the garden with me, showed good comms and no breakup.

So, as long as ive diagnosed that correctly and the fix is good, I now have almost everything I want in my Clansman collection!

Alexanderson Day and SAQ

Sunday 3rd was Alexanderson Day, an annual commemoration of the Alexanderson Alternator, an early form of transmitter that utilized very high revolution rate motor-generators to produce a high power RF signal. Only one of these beasts remains in operation, at SAQ Grimeton, in Sweden. Each year, this VLF transmitter is run up and a message transmitted in CW on 17.2kHz.

The frequency this station operates on is so low that none of my receivers go that low! My FRG-100 will go down to 30kHz. So to receive these signals, a clever trick is used - a fast sample rate sound-card! In this case an extremely cheap Chinese USB device. A long random wire antenna is fed directly to the mic input channel, and then spectrum analysis software used.

This year SAQ transmitted its message at 09:00 and 12:00 UTC. For the first message, I quickly run out one of my Clansman HF antenna wire spools, just draped over everything, little more than 6ft off the ground. This was pretty much ineffective for SAQ, picking up just two of the stronger VLF encrypted naval teletype transmissions.

I realised I needed a vertical component! With a couple of hours until the second transmission, I changed the antenna config to a hastily rigged inverted L. With the connector of the Clansman wire held precariously in the screw thread on my VLF adaptor (actually just some static and overload protection) and wrapped around the door handles and a hook in the eaves, and the far end run up the flagpole, I was now receiving several of the worlds encrypted naval broadcasts.

 And then, at about a quarter to, the first V's were clearly heard! On the spectrogram above, eight teletype broadcasts can be seen, as well as some interference lines. But, over to the left, and below the red marker on the scale, it should be possible to make out a broken trace. This is the spectrogram of SAQs CW transmission.

The message itself, whilst at a speed that I could actually copy, was rather rough sounding and the QRN meant that my rusty Morse was insufficient to copy it. I did manage to pick out bits, including the Tx power of 200kW!

More Contesting!

Well blow me if it isnt the weekend of VHF National Field Day!

After my, ahem, 'success' in last tuesdays 6m UKAC, I decided to have a tune about on 6m and give a point or two away. Well, 6m is utterly dead! Two stations worked! So, I moved to 2m, which entailed a bit of digging to find the BNC for the halo antenna. Despite the Halo being somewhat wonky, and the 30m or so of RG-58 connecting it to the shack knocking me to effectively -6dB SRP (Seriously Reduced Power) as I would ticket it at work, ive made a few QSOs using the 2.5W from my Yaesu FT-290mk1 (an erp of around 800mW!). Buoyed by this success, I made the effort to get the 30W linear amp online, boosting me up to a throbbing 7.5W calculated erp! I really must get a rotator and put the 9-element Tonna up!

The contest doesnt end until 1400UTC tomorrow, so i'll see what there is doing in the morning.

In the morning I also hope to receive the broadcast by SAQ on VLF. Alexanderson day commemorates the development of high speed alternators for telegraphy transmission, with SAQ being the one remaining working example. I'll have to get up early and string up a temporary long wire for it.

For now, a few more spins of the dial as a  'Fixed Station, Sweeper, Restricted', and then off to bed

Unhappy DX-70TH

Ive come home to find that for some reason my PC has logged me out of everything! Ive just had a battle to recover access to this blog! I do hate it when the computer thinks for itself!

Having regained control of the machine, and got access again to my accounts, I was able to see that one of my user groups had a reply to my query about the Tx power settings on my Alinco DX-70TH.

Over the last few days I had noticed a drop in power, to almost half. With a suspicion that the internal power select switch was iffy, I found out the schematics, and put a post on the DX-70 user group asking if anyone else had come across this issue

The switch in question can be seen at the top of the main PCB, just below and left of that big cable tie. Testing all the bands showed a range of power from as low as 30w up to 80w, and generally getting lower the higher the band. In the end it was another members suggestion that he goes up and down the band switch to clear the fault, that resolved the issue for me. It would seem then that its a relay issue. For now, I have full power back!

Ive also been doing some digging about for Clansman audio connectors. I have bids on a couple on ebay, but a rummage through some long forgotten junk at work brought up a new old stock Racal cable with a pair of these 7-pin right angle plugs on!

The cable was about 20m long! Its not now, because as the picture above shows, part of it is already a 5m long 'break-out' cable! These right angle plugs are not really intended for the Clansman PRC-320, and only just fit (they are wider than the usual straight type) but the angle is away from the radio so they are perfectly usable.

I have also had a reply to my post asking for a coding partner - someone to look after the software side of the project. I have yet to reply to him though, something I will do tomorrow! (hope he's not lost interest!). This delay is due to a bitch of a week at work and being essentially knackered on getting home at night! My apologies to him already if he's reading this blog! Ive not forgotten!

Also this weekend, I really must sort the HF antenna mount on the car!

After all, might as well do project work - theres no propagation! Heres todays solar disk -

50MHz UKAC Contest

On arriving home last night from work, somewhat late due to attending a briefing from the glorious leader, I decided to have a bit of a tune around,

which led me to taking part in the last 40 minutes of this months 6m UK Activity Contest, bagging 15 QSOs in that time.

Bearing in mind that not all the results will be in yet, im currently 59th place, out of 66! Not too bad for a small chunk of the contest time and a fixed SSE bearing on a low 3-element Yagi.

Don't be scared of the scrap

Ive been doing a bit of skip-ratting recently. The main purpose of this is to womble up some more sheet aluminium. 19" rack mount equipment will often yield at least one nice big sheet of aluminium, or sometimes galvanised steel, from the covers. All very useful for making boxes and chassis for projects.

Most of the 19" racks units I end up with these days are, even when nominally of 'radio' equipment, digital beasts inside. And almost invariably all SMT! You might think that such things would be of little use in amateur radio.

But thats not the case. Take just one of these units, a now obsolete MPEG2 encoder. Lets take a 'walk' around the unit...

Theres a filtered mains input socket, lots of 75ohm BNC sockets, D type sockets, lots of push buttons and LEDs on the front panel, a very nice big backlit LCD unit. Hundreds of ceramic and electrolytic SMT capacitors, various crystals and crystal oscillator modules, voltage regulators, EMC filters.  On the boards there are SMT ICs that are useful - dual op-amps, SMT fuses and holders, latching relays. There are also numerous broadband RF transformers. So, just because its essentially a load of VLSI digital chips, theres still plenty of parts of use in old fashioned analogue radio building. And, of course, the hardware - M3 nuts, bolts, washers and spacers. Ali sheet, some plain, some perforated. Theres of course very useful high power and EMC clean SMPSUs, theres cooling fans, heatsinks, and connectors. Even some lengths of coax and ribbon cables.

Kit Itch

I feel the need to build a kit again, but really dont have any money spare. Its not so much the need to burn solder, as to bend metal!

So, ive plumbed for another el cheapo Chinese Pixie. I have an idea to knock up a little aluminium sheet cube, with a compartment underneath for the battery. Maybe even, a leaf spring telegraph key on top of the case! A small hole in the top with a plastic shaft down to the frequency pot.

I need to convince Bob M1BBV to get his antenna back up and get his morse key plugged in!

SOTA this weekend - and charity

This weekend, 18-19th June, as close to summer solstice as possible, myself and Bob M1BBV are again walking the Lyke Wake Walk for charity.

We plan to activate SOTA summits G/TW-001 and G/TW-002 at some time on the Sunday 19th, using 2m FM, so listen out for us!

And please, if you can, and especially if youve enjoyed reading my blog or if any of the info has been helpful to you, consider making a small donation to our nominated charity Meningitis Now,

to donate, simply click the link below!

http://uk.virginmoneygiving.com/team/Walkingenglishmen