I installed a 6-BTV vertical about a year ago. It is ground-mounted with about
60 radials and fed with Bury-Flex coax. I felt that the SWR was where I needed
it. Over the winterI saw a shift in the SWR to the high end of most bands. I
suspected that some clamp loosened and a dimension changed. I started to
re-check dimensions and checked all my coax connections and did not see any
problems. I began to suspect a trap leaked or got out of adjustment. As I began
to try re-tuning I found that when I checked SWR with my AIM-4170 analyzer or
an MFJ-259B the SWR showed a the dip at a much higher frequency than I see with
the SWR meter in my radio (tuner bypassed), a K-3, or on an external SWR
bridge. I have to assume the radio should be the preferred tool since the rig
will fold-back if it doesn’t like the SWR. I have tried calibrating the AIM
with standards at the end of the coax and have also used a new run of coax.
My real concern is the lack of consistency between the analyzers, which are
close in readings and the SWR meter at the radio. I have been using my Argonaut
VI and a separate coax to tune but still having difficulty seeing the low point
on several bands. I am looking for ideas of what can cause such a discrepancy
between the analyzers and RF from the radios (typically 5 watts). Any
suggestions appreciated.
Thanks,
Phil N3ZP
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