KL7UW
600 METER DDS VFO 



   N3ZI has made a modified DDS VFO for use on 600 meters that has a 1-Hz resolution and stability.
   I purchased the prototype unit for use with my surplus NDB transmitter in place of crystals.

   Here are some photos of the unit"












   I took it to work and measured the output with an IFR-120 service monitor with frequency stabliliy
   under 1-Hz and drift of less than 1-Hz over several hours.  Absolute frequency accuracy was not 
   measured since the IFR is out of calibration.  Signal level was measured using a scope at 0.3 Volts
   peak-to-peak (0.106 Vrms and -6.5 dBm/50-ohms).

   I built a line amplifier using a 2N915 NPN transistor that has 18-dB gain.  This will provide +10 dBm
   output from the VFO.  The NDB transmitter requires lower input for full drive so a potentiometer
   pad will adjust the drive level from the VFO.



 
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