5 Mar 2011
Whilst playing with VXOs for my 10m DSB transceiver I realised that a cheap 14.060MHz crystal (available widely for about £1-2 each) would make a nice LO source for a 28MHz direct conversion WSPR transceiver. Doubled, the output is easily pulled to 28.1246MHz, the WSPR frequency. The PA does not have to be linear, so all that is needed apart from an oscillator/doubler is a single balanced mixer followed by a small PA. With the DSB approach, half the power is wasted and there would be an audio image 3kHz away on RX. However, the audio stages could be filtered to allow just 1.4-1.6kHz through. The whole transceiver could be extremely simple and stand-alone. I must build one.