28 Feb 2021

Ultra simple transceiver for 10m FT8

One of my ideas is for an ultra simple crystal controlled FT8 transceiver for 10m probably. Another option is 15m. Crystals can be quite expensive, but bought in quantity the price comes way down. 

I have in mind a simple DSB rig at 28.074MHz only, a bit like my WISPY transceiver.  The full transceiver version of WISPY was never built, but both the RX and TX versions were built. I wonder if there is a low cost source of 14.040 (easily pulled) or 14.037MHz crystals? This would be simpler than a synthesised source. I don't think pulled ceramic resonators would be stable enough, but they might be.

My health rather precludes me designing and building one these days, but I would be more than happy to share my ideas with anyone who could take this on seriously. Ideally, a PCB could be made as a simple kit. 

In my mind this could be a really simple rig that would be able to work the world very soon once 10m really gets going. Don't forget that 10m is always good in the Es season at any part of the solar cycle. Even very low power FT8 would get all across the world.  10m is an excellent band with small antennas and QRP. I can imagine such rigs being incredibly simple and low cost. In this version I used a 2N3866 PA, but I would use paralleled 2N3904s as these are far less expensive.  For greater TX power, further 2N3904s PAs could be paralleled with low value emitter resistors.  This is a very low cost way of getting useful output.

Very few controls are necessary, probably none! It would need a BNC connector and probably something to show it is on RX or TX. I can imagine it fitting in a low cost, small, plastic box.

QRPguys are offering something similar on lower frequencies. Maybe they will offer higher frequencies later as the sunspot cycle gathers pace? 

See https://qrpguys.com/ .

UPDATE 2020z:  Steve G1KQH has told me of some low cost crystals that would certainly work: https://kc9on.com/product/14mhz-hc49u-tall-crystals/

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