[aprssig] 144.39 quartz crystal? (was 145.39 crystal)

Jason Winningham 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  
picobeacon: http://www.kd7lmo.net/picobeacon.html

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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