[Lowfer] WD2XES WSPR Again

[Stewart Nelson]

Johan, SM6LKM wrote:
> >beeing a QRPer at heart, I don't like the idea of using a big PC as
> >a QRPp beacon controller so I wrote a MEPT_JT beacon controller
> >program that runs on a PIC. 


Bill de Carle wrote:
> Great idea, Johan.  Using the varactor to pull the xtal frequency
> seems like a long way to go.  Why not just change the phase increment in
> the AD9850?

It seems that one could build a QRP beacon exciter around an old MP3 player.
The exciter would consist of the player, a crystal oscillator and a mixer to
combine the signals.

Most of us have a player that is no longer used, e.g. because its capacity
is 1 GB or less, it has a poor screen or none at all, or it has a lousy UI.
Or, you can buy such a unit for $20 or less.  These players have an
excellent energy footprint, typically running 15 hours on a 1 AH cell.

Two designs come to mind.  One could use the stereo outputs to provide
I and Q signals, which combined with quadrature outputs from a two bit
counter driven by the oscillator, would allow a digital multiplexer to
serve as a very simple image reject mixer.

Alternatively, for LF, one could put the player's audio output at 10 kHz
or higher; the image from a conventional mixer would be at least 20 kHz
away and could be easily removed with a simple filter.

No VFO would be necessary, as the audio frequency would be varied to tune
the band.

This sort of beacon would not be limited to WSPR -- it would work with
almost all signal formats in common use today, and would likely be
compatible with most formats not yet invented.

Static errors in the player's timing could be pre-compensated in the
file loaded in.  Timing drift from temperature changes or aging should
be insignificant for many formats; when sending WSJT you'd have to
restart the player every few days to maintain adequate synchronization
with UTC.

Stewart, KK7KA