Has anyone experienced a significant (approx 100+Hz) and "sudden" drop in
resonant frequency for the 20m band -only- on a Force12 C4XL yagi? This has
happened to mine (ant about ten years in air with no prior problems). Before I
climb tower to investigate, is there something specific I should look for that
may have caused this? 20m is now resonant at 13.980 and was resonant near
14.100. SWR is 1.06:1 at 14.000 (Z/R = 51.7ohms) and at 14.330 1.58:1 (Z=64.2
R=60.1). The antenna is at 72 feet and not been touched since I noted this
sudden change in SWR. Still usable, of course but this change may be an
indication that something is going bad and may get worse if I don't fix it.
Weather is very spring like (60s and sunny) in Midwest, so no issues with
icing. Looking at elements from a distance, they all look normal.
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