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[TowerTalk] Guy-wire resonance solutions

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Subject: [TowerTalk] Guy-wire resonance solutions
From: (Healy, Rus)
Date: Tue, 17 Aug 1999 11:10:52 -0400
If anyone on the list has tried breaking up guy-wire resonances by
installing ferrite beads over the guy wires, I'd like to hear about your
results and, particularly, how you measured the results.

Some background: I'm seeing zero F/B on my Cushcraft 40-2CD that's mounted
at 96 feet, 1 foot above the top set of guys on my rotating tower. I
suspect, after verifying the antenna's dimensions, that the lengths of the
three guys attached to the guy ring--which together act as a capacity hat
along with whatever random electrical length the tower/guy/antenna
combination may be--is the root cause. The former owner of this tower (and
guy wires . . . ) had a similar problem with his Hy-Gain 402 that was
mounted in about the same place on the tower. He and I always attributed
that to a lame electrical design. The Cushcraft is a known performer, so the
jury's still out on the issue. The Hy-Gain was probably fine (except for
those aluminum loading wires!).

The guy segments attached to the tower are roughly 20 feet long before the
first insulator.

Of course, I want to eliminate the problem. The known-good solution involves
attaching temporary guys, releasing the permanent ones and adding extra
insulators close to the tower. For obvious reasons, I'd rather not do it
this way. On the other hand, it's fast and low-risk to slip some split
ferrite beads over the guys a few feet from the tower and see what happens.
I think this will work, but I'd like to hear from anyone who's done this
and, preferably, made real measurements to verify the results.

Thanks in advance!

--73, Rus, K2UA

Rus Healy
Senior Systems Engineer
Adaptive Broadband Corporation
Tel +1-716-242-9600

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