[hpsdr] SDR-1000 /Janus TX noise sidebands

[Al]

  In a previous message, AA8K, in the investigation of his TX noise 
problem mentioned that he saw a HF oscillation on the TX I & Q signal 
coming from Janus.  I do NOT have the same noise problem that Mike has, 
but I was curious about the oscillation on the TX I & Q signal and its 
effect on the spectrum of the SDR-1000. Attached you will find three 
photos.
  The first 'SDR TX w-Janus' is the spectrum of the SDR-1000 when driven 
from Janus. (SDR is in tune mode 10 watts out, The horizontal scale is 1 
Mhz per division ) Notice the broad noise humps. Both a switching power 
supply and an linear power supply have the same noise humps.
  The second is 'SDR TX W-D44' is the spectrum of the SDR-1000 when 
driven from the D44 sound card. Notice the absence of the humps but the 
noise skirt.
  The third is the 'SDR TX W-HP204C' is the spectrum of the SDR-1000 
when the I channel is driven from and HP 204c  audio oscillator at 1 
khz  which produces a double side band signal.  Notice the near absence 
of the noise skirts.

  Although the humps are > 50 db below Peak output and therefore 
probably legal, I think that we should do better.

AL, K0VM

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