We've used this scheme for K4BFT's field day 80/20 CW setup for the past six
or seven years. The 80M inverted vee is supported above a 2el 20m quad which
is at 50 feet. We used two lengths of Radio Shack TV masting just dropped
into the short rotator mast. The upper end of the TV mast has a saw kerf to
allow a hose clamp to tighten around a sealed ball bearing. We used a 12"
eyebolt, with a 90 degree bend, through the bearing, with washers and jam
nuts either side of the inner race. The washers are small enough to clear
the outer race while clamping the eybolt to the inner race. The bent part of
the eyebolt extends 6-8" off to the side, and provides the center support
for the Vee. It's been trouble free, even though we ALWAYS have t'storms;
I've frankly been surprised that the bearings are still free-running seven
years later, after all that rain.
If I were to try this in a more permanent application, though, I'd use two
bearings and protect them from the weather.
Chuck, N4NM
a 2el ----- Original Message -----
From: <thompson@mindspring.com>
To: <towertalk@contesting.com>
Sent: Wednesday, July 07, 1999 11:18 AM
Subject: [TowerTalk] Mounting a dipole above a tower and beam
>
> I passed this info on but in the mid 70's K4SB (Then K4DJC) has an article
> in either ham radio or 73 about mounting an extension pole out the top of
a
> tower using a rotating bearing so that the dipole or any wire antenna
would
> stay in one position while the top section rotated. This would also work
> with the rotating tower version.
>
> The key is to get the extension long enough to clear the beam below. In
> K4SB's case this was 17 feet. The article is cross-referenced in either
> the ARRL antenna book or the ON4UN book or both.
>
> What better way to get the dipole or inverted V higher in the center!
>
> 73 Dave K4JRB
>
>
>
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