[TowerTalk] Guy-wire resonance solutions

[Rajiv Dewan, N2RD]

>From a purely theoretical perspective, as I have no tower, one could use a
quarter wave shorted stub to detune the guys.

Imagine, if you will, a wire 1/4 wave long that is parallel to the guy wire
that is open near the antenna but shorted to the guy at the far end.

One could construct this quite easily in this fashion:

1. Start with a 3 in long stiff stainless steel , drill holes at both ends.
2. Cut an angled slot into one of the holes so that the strip can slipped on
to the guy wire without having to undo the guy wires.
3.  Attach a 1/4 wave long wire to the other hole in the strip.
4. Use twine or rope looped around the strip to position the strip on the
guy wire.
5. A little tension on the attached 1/4 wave wire will secure the strip to
the guy wire.

The velocity factor should be pretty close to 1.

The strip could also be substituted by stiff ss wire, a looped strap, etc.
Whatever you have in your junk box.

Regards,
Rajiv, N2RD

----- Original Message -----
From: Healy, Rus <rhealy@adaptivebroadband.com>
To: <towertalk@contesting.com>
Sent: Tuesday, August 17, 1999 11:10 AM
Subject: [TowerTalk] Guy-wire resonance solutions


>
> 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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