Adding an Artillery Command Post to a Military Vehicle Collection – Part 2 – Radio Considerations

(And Getting Licensed)

So what has this to do with radio?

Having made the decision to start investigating a command vehicle it seemed to make sense to understand what army radio involves. In this regard I am lucky in that a friend is ex REME and was involved in the maintenance and repair of Clansman and Larkspur sets and still works with the MoD on various radio systems. He therefore understands not only the theory but also the practical side and how the equipment was used in service.

Understanding the Clansman Radio Systems and Modules and Using the Working Sets

Once I started the research I soon realised that the whole field is much more complicated than I thought, and that it would be much more involved than I anticipated. Identifying the Clansman sets was quite easy as apart from a few rare and specialised sets, they divide between VHF and HF and between portable and vehicle mounted. Not only that, it is possible to mount portable sets in vehicles without too much difficulty and because the system is modular, instructions and mountings are readily available. The problem is knowing when to use any particular set or frequency and that required an understanding of basic radio theory. This involved many hours of research and discussions until it began to dawn on me that the project was feasible and that some of the sets would actually be capable of use in the amateur bands provided I obtained the correct licence. The next step was to dip my toe in the water and see what I could get.

Locating and Testing Radio Kit and becoming a SWL

The answer to the problem appeared to me to be to find an HF set that covered the amateur frequencies and to get it working. As I did not have the vehicle, a battery operated portable would be ideal, and this narrowed the search down to the PRC 320. I saw two at auction on a site and bought them. With hindsight I probably paid too much, but you learn by your mistakes and they were complete to the CES apart from batteries which I found on eBay. They received very well using the whip and I enjoyed sitting on the patio of an evening just listening to anything that was out there. I was surprised by the distances involved – I have heard Brazil, the United States and many parts of Europe just using the 320 as a man pack without any additional antenna, but I still had no idea whether it worked as a transmitter.

That was fairly easily solved. I took both sets to the War and Peace show at Beltring and a friend of a friend set them both up on his FFR and managed to transmit and receive successfully using the harness and a 4m antenna. I had hoped to be able to sell one there but that did not work out, so they came back with me. I am now considering adapting one to LSB but this is still in its infancy.

Antenna Theory and Practical Work

The next step was to look at the antenna. My ex REME friend pointed me in the direction of various sites about antenna theory, and using those as well as the PRC 320 user manual, I attached 40 odd metres of Kevlar wire to it and draped that all around the garden. Needless to say it was a complete failure and I could discern no difference between that and the whip. Back to the manual and to eBay and I bought a 5.4 metre fibreglass mast. After a bit of tweaking this was set up in the field with the whip attached to the top and the set connected. The test was to listen to the VMARS transmission on a Saturday morning, which I could not do with just the whip on the set, and the proof of success would be to receive this in an audible fashion.

I was surprised, but it worked. I managed to hear the broadcast pretty well – the net controller was extremely clear but what was more interesting was that I could also hear some of the responses from other users. One that sticks in my mind was a PRC 320 user from Conway who came across very well indeed.

More antenna theory and research was needed as even with a 5.4 metre lift it was clear that the whip had its limitations and I needed to look at other options. Draping wire around the garden or across the field did not seem to be the best way, even if this was an option shown in the user handbook, so it was back to eBay and the net. I managed to find an 8 metre telescopic mast and kit for a reasonable amount and the plan was to repeat the VMARS test but using both masts with an end feed antenna between the two. Looking at the tables in the handbook and on the set itself, and running a couple of checks using calculators on the net, a 40 metre length seemed to be the desired option. I ran this out using the tags on the antenna wire and then put up the 8 metre mast. I was surprised how well thought out this was and how easy it was to do by myself . If anything it was a sight easier than the 5.4 metre mast which kept flopping around and dismantling itself. Anyway – both masts were set up and the antenna connected and tensioned. Radio connected and switched on; a bit of a whistle whilst it tuned and then the reception was as clear as a bell. Again the net controller was perfectly clear but this time I could hear many more of the contributors and there seemed to be less in the way of background hiss than before. All in all it was a success and quite exciting.

Becoming Licensed

That is about as far as I have gone with the set at present. I have booked a course with the local Amateur Radio Club which I hope will result in my foundation licence in six weeks time. My research in the meantime will be to look at how I can achieve as much as possible from the set and power that I am allowed and this again points towards making the most efficient antenna that I can. I have set myself some parameters in this and that is that I have to use the material and kit that would have been available to the Army at the time. It would be too easy to use better, civilian kit but my aim with the whole set up is to be as tactical as possible and to live with the compromises that this entails. I have been advised to look at NVIS as one possibility, I am researching Dipoles, end fed, ladders and G5RV antennae and once the weather improves I will conduct some tests to see what works in what circumstances. I hope that the members of the forum and the local club will be able to help and that my knowledge will expand. Watch this space!

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