I think the bigger problem will be leakage. Any leak from the
transmitter BFO will be heard in the receiver. Any leak from the
receiver BFO that gets past the filter will be radiated as a background
signal. I doubt there can be enough shielding and shut off stages to
totally prevent the transmitter BFO from being heard in the receiver
during key up. Not with the BFO running on 9.0004 in the receiver pass
band... You need a mere 100 or 150 dB isolation. That is more than hard
to get in a simple package.
Might be better to mix a 23 and 32 MHz pair of crystals and key the
mixer, you tend to get better isolation from keying a mixer than a
straight through stage, because if you remove the nonlinear element
stray failures of shielding don't yield strong enough signals to produce
the beat product.
73, Jerry, K0CQ
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