Did you attach NEW coax before making the measurements?
Coax, after 20 years, will exhibit some terrible impedance
characteristics!
Second possibility .. those traps might have lots of insect nests in
them .. and they might be shorting the traps.
The only other answer might be .. IF there is a balun .. that the balun
might have taken a lightning strike and be PFFFFFFT.
Don - N8DE
Nat Heatwole wrote:
>
> Hello all. A few months ago I found an old Mosley CL-36-M six element
> tribander atop a local tower. The owner said that I'm free to have the
> beam if I take it down. It has been atop the tower for 20+ years and has
> been thought several hurricanes, ice storms, and busts of high wind and
> has been heavily exposed to rain.
>
> It's not rusted as far as I can tell and it shows no obvious structural
> damage, abnormality, or signs of wear but upon hooking an MFJ Antenna
> Analizer to the feedline I observed some strange results. The SWR's were
> as follows:
>
> 28.000 mhz 4.0 SWR
> 29.000 mhz >25 SWR
> -lowest at 28.134, 3.5 SWR
>
> 21.000 mhz 4.1 SWR
> 21.450 mhz 9.0 SWR
> -lowest at 21.135, 3.3 SWR
>
> 14.000 mhz 8.2 SWR
> 14.350 mhz 16.5 SWR
> -lowest at 14.160, 3.8 SWR
>
> What on earth could cause SWR readings like that? Could it be something
> as simple as a component of the antenna not making contact where it
> should or damaged traps or is it something more complex? The antenna
> shows relative SWR dips in all of the bands, is that significant? What
> are the odds of being able to fix this? All comments greatly
> appreciated.
>
> 73, Nat, WZ3AR
> <nat@ajheatwole.com>
>
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