[hpsdr] Preselectors

[FRANCIS CARCIA]

The Cubic claims it can change frequency in 10 ms. The problem with relays is transients generated as the frequency changes due to relays making and breaking. Even solid state switches could cause transients during wide frequency sweeps. (I hate to admit it, but converting to a high IF with varactor a tuned IF might be the only clean way to sweep wide ranges. Maybe convert to a high IF then at the end convert back down with the same oscillator. Anybody know how to do that with an IP3 of 50 dBM?) 
  Discrete filters,
   A standard board could be built with two different applications depending on parts installed. One configuration for Ham band only and the other for the whole spectrum.
  I've seen a number of SDR posts in different places where guys build brick wall preselectors to improve performance.
  I think the preselector should be in a shielded box away from digital noise or I'm about to leard some cool PCB layout skills from a master. fc
   
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