WISPY 10m WSPR

What it is

WISPY is a simple DSB beacon transmitter for 10m WSPR. The idea was to use a low cost 14.060 crystal, available from many sources, in an oscillator-doubler circuit feeding a diode single balanced mixer and small low cost PA. The latest PA version has 4 2N3904 transistors in a class A stage producing over 500mW pep DSB (250mW SSB equivalent in the WSPR band) although the schematic shows only 2 devices in the PA and produces around 100mW in the WSPR band.

A small RF indicator is included to light up a front panel LED when the TX sequence occurs. Since increasing the power, results have been very good with spots worldwide from as far away as Australia.

Breadboard Construction

This WSPR beacon frees up the FT817 for other purposes as I can still send WSPR on 10m whenever I am at home and have the PC turned on.

As I often do, WISPY is built on a piece of copper laminate using MeSquares available from QRPme.com . This sort of construction is excellent for RF circuits as it provides a really good solid ground plane and reduces the chances of spurious emissions and instability.

Please note there is an error on the schematic. Where it says 9t this should be 22t. I have no means of changing this!

Full Transceiver WISPY

A full transceive version of WISPY has been breadboarded in separate sections but has still to be boxed and tested. The schematic below should work, but caveats apply! Basically the idea is to buffer the crystal oscillator stage and feed this into a Polykov mixer (injection at half frequency). This receiver HAS been tested but, as I said, the whole lot has not been built on one board yet.

There is no real reason why this design could not be used for PSK31 and FT8 as well.

UPDATE 24th May 2021: There is an error on the circuit below!! On the main toroid it should be 22 turns and NOT 9 turns.