Assuming you safe using the same length of coax to the rig and the
analyzers, maybe the coax has an imperfection that only shows up at higher
power? I check coax with opposite e d open (such as gamma match), with a
digital ohm meter. If you hVe megohms of resistance, you a e bad coax.
Chuck W5PR
On Tuesday, June 23, 2015, Phillip Zminda <phil-z@comcast.net> wrote:
> 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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