[BC] Harris SX-1 Spur Problem

[Lewis Munn]

Dunno if this will help any, but I had an SX-1 down for a considerble length of time due to a spurious glitch in the envelope waveform.  It actually showed up as a notch in the envelope, just after the peak.  At full power and modulation.  At lower values it was an oscillation at an ultrasonic frequency on the envelope wveform.  Got progressively worse.
   
  Final cure, after replacing lots of parts and several sets of FETs, was to increase the RF drive out of the IPA by about 20%...and this put it above book, btw.  Transmitter has been running fine ever since.
   
  I have no explanation, and Harris has hardly anybody who can give more support than telling me to check if the circuit breakers are on, and so on...reading the installation procedure.
   
  In the one I was looking at, the + supply for the IPA was at the factory setting of ground.  I went partway up on the + side of the voltge divider, and the problem rapidly went away after hitting a threshold.
   
  Maybe you are having the start of the problem I had??  Just a thought.  Sorry I cannot tell you any parts to replace that made any difference at all.
   
  Looey Munn
  Roundup, MT
  

gRAdy Moates <lists at loudandclean.com> wrote:
  I know of an SX-5 with the same problem. . . in the
same condition. . . we've been working on it regularly. . .

		
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