Tuesday, 1 November 2016

Clansman PRC-349 on 6m?

The PRC-349 is generally shunned by the amateur community, being as it is the bog-brush haired back-stairs sprog of the Clansman range. Its quarter of a watt output power is mediocre at best, and its 150Hz tone squelch system makes it awkward to interwork with non-Clansman radios. But perhaps its biggest drawback is that it doesnt cover any amateur bands.

Shame really,

But should this be the end? Why cant it be converted? This is something ive been looking into.

There are a number of problems that would need to be overcome in order to move the 349 to somewhere it might be useful -

- Its coverage 37 to 46.975MHz
- Its tone squelch system
- Its 25kHz steps

Lets look at each of these in turn,

Coverage - ok, so its a good way from anywhere, but, the move to 6m (50MHz) from 46MHz isnt too far, and the front end might just adjust, if not, it shouldnt be too hard to retune.

Tone Squelch - The squelch system needs to see a 150Hz tone at >3mV at the discriminator output. Hmmm, shouldnt be too hard to inject a suitable tone here

25kHz steps - ok, so this is harder. But - we would also need to pretty much replace the Tx and Rx VCOs and the synthesiser anyway to convert the set, so the new control system would just be built for 10kHz steps as required.

Heres my thoughts - Replace the synthesiser and the VCOs with an Arduino Nano, and a DDS module. Most DDS modules have multiple outputs so one for Rx and one for Tx. The original switches could be reused, or other suitable types fitted to get easily selectable steps. The Arduino takes care of all that. The Tx mic audio would need to be modulated onto the Tx side of the DDS, I believe this is not too hard to do. Some waveform shaping I think might be needed though. The Arduino can generate the tone to defeat the squelch.

Perhaps a trial on the bench might be in order...

No comments: