Date: Mon, 20 Feb 2017 23:03:55 -0500
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] tower/rotator woes...
And you torque balance a bank of 440 antennas with rear mounts, how?
They were no problem with the dual worm gear rotator.
Unfortunately they were what I had.
73, Roger (K8RI)
## Good point. You could use a rear mount array on same or other freq,
pointed 180 deg in opposite direction. Then mentally add or subtract 180 deg
from the rotor heading.
## Or perhaps use a tq comp plate, rear mounted, or on a short length of
material,
on the same mast, but pointed 180 deg opposite to your rear mount 440 ant.
## The only issue with any tq comp plate scheme is it does add more total
wind load
to the boom. Like on a 20m long boom yagi, with els bunched up at the REF end
of the boom. For every one foot the boom to mast position is changed, the
difference
between REF side of boom to the DIR side of boom is doubled. IE 40 ft boom,
and boom to mast plate located 17 ft from REF. Other end of boom is now 23
ft long.
Mast to boom plate located at 19 ft, other end is now 21 ft long, a 2 ft
difference, for just
a one foot shift. Watch out, the long end of the boom has a lot more stress
on it, when broadside
to the wind.
## another way to achieve tq comp is to route the coax either on top of boom,
or below the
boom. Coax, plus any balun, will in some cases, act as a tq comp. LMR 600
or even 213
taped below a 2 or 3 inch boom, makes the boom look bigger diam to the
broadside wind.
The effect of coax routed that way, plus any balun, will allow for a smaller
sail area on any
tq comp plate.
## You cam also mount at boom center, then add a counter weight at light end
of boom.
You can also use a combo of coax, balun, smaller than normal tq comp plate, and
lighter
than normal counter balance weight.
## any scheme is better than nothing, even if you dont achieve perfect tq
balance .
Takes the stress of the rotor, both rotating..and stopped.
Jim VE7RF
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