[AMPS] SB-220 input circuit

[Peter Chadwick]

Tom says:

>It doesn't make any difference what the source is, transistor or 
>tube, in setting SWR.

I agree with Tom, but there is a caveat awaiting the unwary. Some of the
earlier solid state rigs (Atlas 210 for example) were touchy about the
antenna matching network that was used. A pi network, giving low impedance
input on frequencies higher than the operating frequency, found it stable. A
T match with inductive input found it unstable on 21MHz, EVEN though the
match was 1:1 at the operating frequency. I guess these days that
manufacturers have checked for PA stability for all angles/magnitudes of
load at frequencies well away from the operating frequency, but I wouldn't
always bet on it.

Certainly, it's worth doing a stability analysis on the solid state beast.
Tubes are much easier......

73

Peter G3RZP


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