There are two virtually identical stages in my Corsair II schematic. The
RF stage and the first IF stage, both high dynamic range transformer
feedback (Anzac patent) bipolar stages using CATV rf power transistors.
One is switched in and out before the mixer, the other is after the
mixer providing the mixer with a low noise and very broad band IF so the
mixer is properly terminated at most of its outputs. That's the secret
to keeping the double balanced mixer working with low loss and great
high end dynamic range. A point lost in Japan in many radios that
terminate the IF port of the balanced mixer with a crystal filter. And
then they wonder how the IMD got so bad.
73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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