[Elecraft] KPA100 TR Switch isolation problem

[Robert Friess]

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