Sub-harmonic mixer based 10m WSPR transceiver

My favourite HF band is 28MHz and I often put my FT817 on and run WSPR in the background whilst getting on with other things in the shack. You may be surprised how often good DX reports are received. This ties up the FT817 so I have been rethinking how to make a very simple WSPR transceiver for 28.1246MHz.

One neat idea is to use a 14.060MHz crystal (cheap from GQRP) pulled up to 14.0623MHz (it is possible) and use this to drive a Polyakov sub-harmonic mixer, which needs half frequency drive, in a simple direct conversion receiver feeding a PC sound card via an isolating transformer. The same oscillator, doubled would be fed into a single balanced DSB modulator and a small QRP PA stage. The resulting WSPR signal would appear as a DSB signal , not SSB, so half the power would be wasted but who cares with milliwatts?

The resulting full WSPR transceiver would be extremely small and simple, need no VFO or VXO and could be left running almost continuously when the PC is switched on. This would be ideal with a small netbook PC.

The idea is not new: see for example http://www.qsl.net/d/dl1gsj/html/qrssrx30.html .

Sounds like this is my next project......