Friday, July 3, 2009

WSPR/QRSS transceivers

WSPR is fun, and not only, it make some sense, propagation phenomena can be looked at decently.
However, having the band of own WSPR activity blocked is bad enough, even worse, having a transceiver blocked...

For 30m-WSPR, Gene (W3PM,GM4YRE) made a nice design, check this out. Nice ideas, however, I would/will do one or the other thing in a different way. Nevertheless, the basic idea is to create a DSB-signal, with some sideband separation by a simple single crystal filter. My present design ideas will not fall short of digital ICs and probably something subharmonic...

For 20m however, another nice option is available with a combination of standard computer crystals for a superhet design.
With a carrier frequency of 14,095.6kHz, the obvious choice would be a 4,096kHz and a 10,000kHz crystal. Either one could serve as I.F. in a ladder-filter. However, I found some 4,068.5kHz crystals, thus, for my attempt, 10,000kHz will be the I.F., allowing for a second frequency suiting the 20m PSK31 range.
Additional option: add yet another crystal and be ready for the 20m QRSS band, yep, that would then be a 4,000kHz crystal.
The next building project is in the queue.

QRT for now, "back to the drawing board" if you want ;-)