I modeled the switch and have identified the source of the problem. There
is a resonance formed between the junction capacity of D12, D14 and the
100uH inductor RFC3. When you add the 12pF cap or a scope probe, all you do
is move it around a little. The easiest way to kill this problem forever is
to replace RFC3 with a 1K resistor. That will introduce an additional
receive path loss of 0.216 dB which is negligable. Try it and let me know
what you see.
Bob
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