Interesting thread.
I remember once I put up an 80 meter dipole and used some plastic closeline
on one end (without an insulator) to hoist it up into the tree.
I went into the shack, test the SWR and all was be fine. Turned the amp on
and SWR went all to heck.
When I checked the rope, I could see where it had been burned. I cut it
off, re-tied it to the antenna and hoisted it back up. Same thing - low
power it was fine, high power the SWR went out of sight.
Then it dawned on me that this clothesline had some wire inside. When it
burned through the insulation of the rope, it added about 50 feet to the
end of the antenna :-).
You would have thought I'd have seen this right off the bat! 73
Tom
W7WHY
On Tue, Nov 29, 2016 at 11:26 AM, Jim Brown <jim@audiosystemsgroup.com>
wrote:
> Yes. I first ran into this nearly ten years ago with the first 160/80
> dipole that I rigged between trees. Like a dummy, I failed to use an
> insulator between the ends of the dipole and the 5/16-in rope. When it got
> wet, the rope melted and the dipole was on the ground.
>
> The ends of any wire are a high voltage point, and should be treated as
> such. This is also true of radials!
>
> 73, Jim K9YC
>
> On Tue,11/29/2016 9:23 AM, Jeff DePolo wrote:
>
>> In high-power broadcast, we regularly see burn-outs caused by weather-worn
>> fiberglass insulators that start to wick up water when it rains. What
>> used
>> to be mostly RF-transparent when dry becomes lossy when wet, with airborne
>> contaminants, rust/oxidation, and whatever else aggravating the condition
>> over time, ultimately leading to arc-over and/or mechanical failure.
>>
>
>
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