By Gordon Bubb G7KNS
With my well-known love of green (ex-military) radios this summer, I came by a C13 set. This is a British Army set in what is known as the Larkspur range, which puts it into use mainly in the 1960s and 1970s. It is of course full of valves. It is a mobile set designed for soft skin and armoured vehicles and is built like a tank. It takes me two hands to lift the power supply and another two to lift the set itself. It is an primarily an Amplitude Modulation (AM) and Continuous Wave (CW) HF set going from 1.5 up to 12 MHz although it will also do Phase Modulation (PM) which the army thought might be useful. It wasn’t. The nominal power output was 10 watts on AM and 20 on PM and CW.
So quite useful for an amateur as it will do top band, 80m and 60m and 40m. And mobile of course if you have a 24v system in your car capable of 6 amps.
The Larkspur range – both VHF and HF – was a major technical advance over previous wartime sets such as the WS19. The cases were hermetically sealed and strong enough to stand on, indeed in a number of armoured vehicles you stand on the radio to get in. All the sets in the range had built in crystal calibrators for their Variable Frequency Oscillator (VFO) tuning, removing the need for separate calibrators for accurate tuning.
Tuning the set is a multi-stage process similar to amateur sets such as the Yaesu FT101. At each stage one tunes the relevant control for a centre zero in the tuning meter. This is unlike the usual amateur set such as the FT101 where one tunes the various stages for a maximum or minimum on the meter.
My set, on receipt, worked pretty well considering the age, one tuning stage does not do the centre zero bit properly and it does not work on AM. CW and PM are OK.
Last week I acquired another one – not for me this time but for the Saladin armoured car at Hever Castle. This set was recovered from a target wreck in Kuwait shortly before the first Gulf War and shipped back to this country. So, plug it in, turn it on and it also works, more or less. It does produce power on AM so there is scope here for making a good one out of the two. It also gave me a belt (175v) so it needs looking into.
Neither have not been opened up yet so watch this space for future developments.
Finally we need an aerial tuning unit for one of the sets if you happen to know of one. Beware, they are hot from a radiation stand point. Do not take them apart unless you really, really have to. And here is one of the beasts, less all the interconnect cables: