[aprssig] 144.39 quartz crystal? (was 145.39 crystal)
jdw at eng.uah.edu
Tue Oct 17 11:06:00 CDT 2006
For not a lot more than a custom crystal ($25 single unit price at
DigiKey) you can get an AD9954 direct digital synthesis chip and
generate RF signals up to 160MHz directly. 9600 baud FSK would be
nearly trivial with this device, and 1200 baud AFSK is doable. KD7LMO
picked out a harmonic and amplified that to use it on 70cm on the
You need a microcontroller to drive it, but you're gonna have a
microcontroller anyway if you're building a tracker or weather station.
One could also use this device in place of a crystal (which I think
is the intent), but for digital TX only it looks a lot easier to jump
straight to the final output waveform.
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