Clansman Manpacks for Amateur Use - Part 4

So you have your radio but so far cant do anything with it, not even tell if it works, because you need - audio ancillaries! We will talk about those in this post, plus a few other bits and bobs, but first, a word from our sponsors -

Army Radio Sales

PTS Norfolk

Alright, so they are not really sponsors, its not like they have given me anything to plug them on my blog (yet - you know where I am fellas ;-)  ), but I ought to mention them as good suppliers of Clansman radios and spares, if only because I have quite blatantly nicked their photos for this post!

So, on to the audio!

Whichever radio you have, you will need some way to hear it and to talk on it. This is the one area where almost all Clansman equipment is the same - the audio ancillaries are all interchangeable. This is great as sometimes one type is better than another different set-up. For instance I like the standard headset for my PRC-320 if its on my back, but prefer a handset for fixed use.

Handset

The handset is probably the simplest to use, as its used just like a telephone, only theres a PTT (pressel) on the handle.

You may recall my cable-less handset - this is a 'Remote' handset, intended to be connected to the radio from a distance of up to 3km using telephone wire (properly DON-10, but at a push whatever is to hand). The PRC-351/2 can do this natively, theres a pair of terminals on it. This allows the radio to be used from a distance, ideal when the enemy DF you and mortar the position you left the radio in (not too likely for amateur use outside of Barnsley), but also as an intercom between the handset and the radio.

Headsets

sets... for yer 'ead!  Probably the most common accessory you will find supplied with PRC-351s. Most will be the 'Lightweight, Infantry' type shown below on Desperate Dan

These are ok, an advantage they have is that the two earpieces are independent channels, and one of them can be popped out to make hearing whats going on around you easier. The idea of the independent channels is so that when used in an AFV the radio can be in one ear, and the commanders intercom shouting at you in the other. The radios have both audio channels in parallel, so unless you run them through the various vehicle intercom boxes, you will get the radio audio from both earpieces anyway.

Another headset style is the Armoured vehicle type below, designed to be used with a tankies helmet (not to be confused with his Bobbies Helmet!)

Neither headset is any use on its own, as they dont have an integral PTT. So you must make sure you get a Pressel cable with them -

 More commonly used with the PRC-349, there is the single earpiece Throat Mic

Not too bad but you do have to strap the mic around your neck! so they are quite unpopular as a result. There is also the Single Transducer Earpiece, shown in the black and white below. Quite unusual, and seemingly issued with the PRC-319, this has an integral PTT on the top, and uses bone conduction for your voice - this means that your transmission goes out sounding the way YOU think you sound, not how others actually hear you! Expect people to not recognise your voice!

And thats most of your audio options. If you can afford one, a freestanding loudspeaker is nice to have for the PRC-320 in particular

 There are also audio extension cables available that allow you to use the radios from around 10m away.

You may also find microphones on their own, with an odd three pin plug on them. You dont need one of these (even if you discover the matching socket on the headset) unless your intending to play ham radio in State 3 Romeo, which to those uninitiated into the world of NBC Warfare (Nuclear, Biological, Chemical) means wearing full chemical warfare clothing and respirator. This mic is the respirator mic - intended to fit on the speech capsule of your gas mask! No, I dont have one of these mics (although I DO have my S10 respirator!)

If you have a PRC-320 or 319, you might also like a Morse key! There are a few types available. Mine is a fully enclosed Racal thigh key (ie it straps to your leg!). The usual Clansman thigh key has a couple of adjusters on top.

So all thats left now is to discuss antennas!

Lots of new readers?

Ive noticed in the last few days, seemingly since I started the Clansman articles, that my daily readership stats have rocketed! Now, this could of course just be the ol' bots crawling over my musings, but perhaps - and stranger things have happened! - just perhaps, its actually real people reading this?

Are you one of these real persons? You all dont say much, but I know your out there I can hear you breathing! Why not pop a comment on? Let me know what your liking about the blog.

Clansman Manpacks for Amateur Use - Part 3

Ok then, back to the basics of the Clansman series manpack radios. Firstly, a word or two about...

SURF (Selector Unit Radio Frequency)

Heres what to do if you think you need a SURF - Forget it!

The Selector Unit Radio Frequency is one of those devices which, particularly the 4W SURF for the PRC-351, you will be offered. You dont need one! In fact, it can even make your signal worse! The purpose of a SURF is to prevent adjacent channel interference or receiver blocking when two or more radios are used very close together physically - for example in a command post bunker. It is simply a preselector. If your going for the 'CES' look (Complete Equipment Specification) for a collection or re-enactment, or to equip your newly restored FFR Landrover (Fitted For Radio, not to be confused with most MoD hardware acquisitions of the last two decades - FFBNW - Fitted For But Not With) then by all means put a 4W SURF on the top of your PRC-351 (I have!) but dont use it for actual on the air operation.

4W SURF

PRC-350 with SURF

SURFs are also available for the PRC-320 (only ever seen one and that was on a table at the Finningley Rally today!) and the PRC-350.

PRC-320 SURF

Don't confuse the SURF with the TURF - Tuning Unit Radio Frequency! TURFs are what we amateurs call ATUs! You will not see them for the usual manpack range, they are more of a VRC (Vehicle) item. But the PRC-319 has one, which is automatic. Likewise, the PRC-351/2 when used in a vehicle can be used with the TUAAM, which is a VHF automatic TURF unit (Tuning Unit Automatic Antenna Matching).

While we are on RF accessories, i'll mention the 20W amp that turns a 4W PRC-351 into ...

PRC-352 20W

The PRC-351 when used with the clip on 20W amplifier becomes designated the PRC-352. At this point, you must start using proper antennas not the battle whips. If you do use the amp, make sure you physically remove the whip, otherwise the resulting dual radiation and poor impedance match causes poor performance.

20W amplifier block

The amp clips on to the bottom of the PRC-351 where the battery was, and the battery then clips to the bottom of the amp. An 18inch long coax cable connects the two. There is a waveband select switch on the amp which must be set for the frequency in use, but thats about it.

So, if you have got yourself a Clansman radio, be it a 320 for HF, or a 350 or 351, even a 352, for VHF, your almost ready to go. But not quite. You now need a power source - a battery. But, unlike modern amateur equipment, you still cant then just turn it on and go. You need audio ancillaries!

Batteries

I wont put pictures of batteries up, as you can easily find these on the blog, and besides you have hopefully got the seller to throw one in!

Both the PRC-320 and PRC-351/2, and the PRC-319, use the standard 24V NiCd packs. These come in two current flavours - 1Ahr and 4Ahr (some variations do exist) and either plastic or alloy cases. The alloy cased batteries are easiest to strip to build modern batteries into. The 1Ahr is about half the size of the 4Ahr. There is even a primary lithium version available.

These batteries of course need a charger. The standard charger is the DCCU, but 12V fed DCCUs are hard to find and expensive. Most are 24V for vehicle use. It is much easier to charge them using a modern intelligent charger that can do all your batteries, such as the Turnigy Accucel-8 I use.

The PRC-350 uses a special and unique 15V battery. Most likely you will get a battery cassette, to take D cells. Invest in some NiMH cells for this, as using alkalines will cost a fortune. Likewise the PRC-349s use an odd 12V 600mAh pack, and if you did get one of these radios you'd most likely get a cassette with it. Incidentally ive got hundreds of these...

I'll talk about audio ancillaries in the next entry. This is quite a wide subject.

Over the past few days ive had my EKGSA antenna rigged on one of my 5.4m masts. This had to come down today, and did so shortly after the heavy showers. Luckily the showers held of for the duration of the Finningley clubs radio rally.

It was great wandering around in the sunshine deciding what junk I could get away with taking home! In the end though, I bought very little - a surface mount relay, and a Clansman Remote Handset.

You might notice that the handset has no cable... find out why in the next thrilling installment!

Lazy radio day tomorrow?

With the nice weather, and some time off, I might decide to have a lazy day tomorrow, just sitting in the garden, reading and playing radio.

If I do, i'll put one of the 5.4m masts up with the EKGSA antenna for the PRC-352, probably also a dipole for the PRC-320.

Another thing I will do, is try pre-measuring the guy lines for the mast. It is possible to arrange the mast and guys in such a way, and with such pre-set lengths, that only a single person is needed to pull the mast upright and secure it. So long as the load on the mast head is not great, this could be done by a reasonably strong person.

Good use for old dead batteries - Eliminators

ok, ok, yes I will get around to the next installment of the Clansman Manpacks for Amateur Radio article, maybe tomorrow i'll cover SURFs, Audio ancillaries and batteries. The final article will cover antennas and masts.

In the meantime, ive been working on sorting and testing the large number of 12V NiCd PRC-349 battery packs ive obtained.

Theres about a third of them in this photo.  Those top left tested over 10V terminal voltage. Those top middle between 1 and 10V.  The few at the right are a dry cell cassette, and a pair of good 15V Lithiums!

Inevitably, from how I came about these, there were going to be a large number that are dead. Most of these will end up going for recycling, after any good terminals have been salvaged. However, a very sensible thing to do with a couple of dead battery packs, especially for specialist devices, is to turn them into battery eliminators! I used to do this for the Kenwood radios I serviced when I worked for NTL, an eliminator allows you to power the radio from a mains PSU and makes alignment easier, as you dont have to ensure your using a good battery!

The first thing to do when making a battery eliminator is to find a dead battery that otherwise is sound, one with a duff cell but good case and contacts. The next step is probably the hardest part and the one that takes the most skill - opening the case. Here its good to have a few that you dont mind smashing while you work out the method! In the case of the 349 batteries, I found they are lightly glued around the top, which is recessed. A few gentle strikes around the seal with a sharp chisel and I was able to pry the top off.

Actually prying the top up was hard as the inside is packed with expanded polyurethane foam. Gently easing this foam out, expanding the gaps etc took a long time but eventually I was able to pull out the cells. Incidentally, the central tube should be possible to push out to give space to dislodge the cells. I'll try that trick on the next one I build. Remember to recycle the cells!

With all the old cells removed and the foam scraped out, I was left with the collection of parts shown below. This also shows the 4mm terminals and the fuse holder.

A bit of marking next and then drilling to create the three holes needed. Tightening the nuts for the sockets and fuse holder is a nightmare as there is simply no clearance inside the pack. Those for the sockets I managed to get tight, but the fuse holder is actually held in place by hot-melt glue!

Once all the innards are installed and wired up, a task that is best done by soldering the wires with the parts outside the case, and threading them through the holes, remembering also to thread the wires through the nuts, the wires were soldered to the terminals and the case closed. The tube was then pushed back in place. Both the tube and the top I secured with a little impact adhesive. Do remember to test the thing before gluing!

The final tasks were to push the securing bolt back into the tube, and fit a fuse. This should be a 1A fast blow type (20mm glass in my case), although its currently a 5A slow-blow in mine as thats all I had!

Another option is to install a grommet and trailing wires rather than sockets, i'll do the next one that way.

One of the 1Ahr NiCd packs for the PRC-320/-351 etc would convert into a very nice eliminator, but would require a 24V PSU. Another option there is to use a metal cased 4Ahr pack, and install a small 24v SMPSU and an IEC mains socket!

Clansman Manpacks for Amateur Use - Part 2

In my previous post we discussed the unusable for amateur radio sets from the Clansman range, and the 'rare' but usable radios.

This time, we'll move on to the most suitable of the series, but starting with the 'least' suitable of them!

PRC-350

The PRC-350 is a 2W FM radio covering 36 to 57MHz in 25kHz steps. This means it covers the 6m band. Sadly, the current 6m bandplan uses 10kHz steps, which means only a few of the -350's channels coincide with a usable amateur frequency, and the FM calling channel is not one of them! It also uses a special 15v battery that is not compatible with any of the other radios. However, its does use the standard Clansman audio ancilliaries, and its antennas are the same as those of the more useful PRC-351. It does however have an internal 160Hz subtone generator which means it will work with non-clansman radios. As with the other radios we will talk about in this post, it also has dual audio connections. Originally, this was so that the operator could use the radio, usually with a headset, whilst a handset was available for the officer! There is also a mini-BNC antenna connector that allows this radio to be used with external antennas for increased range.


PRC-351

Of the VHF FM Clansman radios, the PRC-351 is understandably the most popular and most usable. Antenna compatible with the 350, battery and audio ancilliaries compatible with the PRC-320, it is a 4W FM set covering 30 to 77MHz in two seemless switching ranges at 25kHz channel steps. This means that although just like the 350 it is difficult to use on 6m, there are more channels usable on 4m, and this includes the calling channel on 70.450MHz. It is also possible, with a simple but tricky to carry out modification, capable of being made to cover a bit of the FM portion of the 10m band, by using a switch to 'fool' the synthesizer!

As with the 350, the 351 has an external antenna connection, in this case a proper BNC. This can be used with a number of Clansman antennas, which we will discuss later, or of course amateur antennas. But its main advantage is to connect it to a clip on 20W amplifier.

PRC-352 - The 351 plus 20W Amp

Adding on the 20W amplifier to the 351 redesignates it the PRC-352. At this point, the various whip antennas can no longer be used and an external antenna is required, but range is considerably increased. I myself have used my 352 and the Ground Spike Antenna to contact Bob M1BBV up on the summit of Ingleborough in the Yorkshire Dales, from Emley Moor, a distance of about 45 miles.

You may notice my PRC-352 above has another unit on top - a 4W SURF. We will mention these later. For amateur use, there is no advantage in having a SURF unit, if anything, they will actually reduce your signal!

PRC-320

The PRC-320 is the most popular of the Clansman manpack series, and with good reason. Build like the proverbial brick outhouse, the 320 is a 30W HF transceiver, capable of CW, AM and SSB opertion in 100Hz steps from 2MHz to 30MHz. Due to its rather agressive VOGAD mic amp, its 30W sounds more like 100W! Its built in manual ATU can match the radio to almost any antenna, although its best suited to capacitve (ie short) antennas. Only capable of USB 'as is', a relatively simple mod can add LSB capability. It does have a few curiosities in its operation, the chief of which is a 2kHz offset (the side-step) on SSB operation. Battery and audio ancilliaries compatible with the 351. However, unless you intend to use it only with resonant antennas, the 2.5m whip and the antenna gooseneck adapter are essential accessories. A tuning guide plate is attached to the radio body which shows what ATU settings are needed for various antennas, or what lengths of antenna wire for dipoles. A pair of clansman antenna wire spools, and a dipole center,  are pretty much also essential accessories.

Prices for these vary considerably. A thick fin version is sometimes available, with reinforced protective fins over the controls, but commands a higher price. Budget radios can be had for less money, but expect some fins to be missing.

In the next post in this series, i'll talk about the antenna, battery and audio ancillaries suitable for use with the PRC-320, 351 and 352 radios.

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 -