That it dropped (from an unstated resonance), in simple terms would seem
to indicate (excluding radiator wire stretch or contact/induction with
other objects) a change in the counterpoise. Some rot, rust, tiny
livestock damage (moles) or other disconnect would be places to start
looking. It could even be at the feed with bimetal reactions... failed
CMC at the feed... some may not be visible (trust me on this one).
Questions: was it a sudden, radical shift (something broke) or gradual
(something rusted away)? Does it seem seasonal or temperature related
(consistent is the best answer)?
One more vote for measuring at the antenna feed, exclude the coax entirely.
Rick nhc
On 12/1/2018 12:39 PM, David Gilbert wrote:
The fact that the resonance has dropped is odd, since it implies more
length instead of less like you'd get with a bad connection. I wonder
if the end of the wire that is in the tree has lost it's insulation
and there is actually contact to wet wood there. That would add both
additional loading and loss.
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