[hpsdr] ALEX

[FRANCIS CARCIA]

Ham Band filters are a good idea but I would like to be able to surf the whole spectrum.
  This would be useful for using this as a spectrum analyzer for testing homebrew circuits.
  I would like to use my Cubic pre-post filter. There are a number of these  floating around the surplus market that have a 10% bandwidth and 40 dB of rejection over the 1.6 to 30 mhz range. They were made by Harris Rockwell Collins, Transworld and Cubic The control is BCD in 10 KHz steps so you need 4- 4 bit BCD words to control the preselector. Also there is a built in TR relay so that may also require a bit of control.
  These bits could also control a led dispaly. I would like to see a latch included so I could control this preselector. The latch would hold the center frequency. This could be used by others who might want to decode it for say antenna selection or roll their own tuned preselector..
  MMIC amps in the 6m  and maybe 10m filter outputs are a good idea and they can be turned on with the switch controlling the channel. 
   
  Unbiased diodes hanging off the antenna could be a source of IMD when strong signals are present. Racal sets the bias on the RA6830 limiter so clipping starts at around plus or minus 5 volts. I have also seen pin diodes used as limiters but may also require some bias. I can scan the schematic of the RA6830 limiter if anyone wants to look at it. I think the Harris RF590 also has something on the input I will check out.  gfz
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