Tom W8JI says:
>Changes in SWR with power level indicate one of three things.
>
>A poorly working SWR meter.
>An arc someplace or a connection or component breaking down.
>A rig that is generating harmonics or other spurious signals when
>power is increased.
A fourth one that I've found is current on the outside of the coax.
Which doesn't make much sense, but probably because at low levels the
detectors in the SWR meter are running in the square law region, so as
the power comes up, the detection efficiency for the total RF power
(vector sum of currents on inside and outside of the braid) changes. [
All this I guess is just amplifying Tom's comment on apoorly working SWR
meter}] Under these circumstances, a balun might help. And it might be
more than one of the above simultaneously.
73
Peter G3RZP
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