Wednesday, October 28, 2009

22m Hifer RX (TX)

Super-heterodyne or not, that is the question. The 22m band is wide, that would not really encourage a superhet design with a crystal filter, at least not when all of the band is to be observed as a spectrum.
Thus, here come the crystal combinations (what did you think???):
  • 6.5536 + 7.000 = 13.5536
  • 6.5536 + 7.005 = 13.5586
  • 6.5536 + 7.015 = 13.5686
Spot on, I would say. For a DC-RX, I would consider to slightly pull one of the crystal and mix. This would possibly enable to observe the full 22m range.

The superhet solution would probably point towards a 6.5536MHz IF, since those crystal are certainly cheaper.

The nice thing on this combi is, there is a ceramic resonator available (7.02MHz), which can easily be pulled in an oscillator circuit.

Source for the crystals and the resonator: