I would suspect an intermittent connection... either a coax connector or
maybe a joint between tower sections. You should bridge the sections
with straps. Also the rotator bearings should be bridged with straps...
anything that could provide a marginal connection.
Larry N8LP
Bill Coleman wrote:
>I'm having trouble with my shunt-fed 15m tower. I have an L matching
>network that is switched between 80 and 160m. A relay selects
>different taps on the inductor, and also adds capacitance for 160m.
>
>If I use an MFJ 259 antenna analyzer, I can get a nice match on
>either band. And if I transmit with a few watts, I have no problem.
>Even the 20 watts that the KAT100 uses isn't a problem.
>
>However, if I transmit about 70 watts or more, the SWR suddenly
>shifts to 3:1 or worse. It changes with each transmission.
>
>I thought the caps might be arcing, so I replaced one of them with a
>wide-spaced variable, same problem.
>
>Any suggestions?
>
>
>Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
>Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
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