To be clear, just because the SWR gets better lower in frequency (to a 50
Ohm input) doesn't mean something has lengthened. It just means that a
frequency dependent impedance has shifted lower in frequency to give the
desired match.
My guess is that the hairpin coil has started to rust and has added
resistance but is still connected. You could test that theory a bit by
putting a carrier on it for 30 seconds and see if the SWR moves. Or the
balun could have a similar defect.
As KK9A said, if the loading wires disconnected or the hairpin disconnected,
the response would be typically a higher shift rather than lower.
Ed N1UR
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