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[TowerTalk] electrically operated vertical antenna raiser

To: "Towertalk" <>
Subject: [TowerTalk] electrically operated vertical antenna raiser
From: Jim Lux <>
Date: Sun, 07 Jan 2007 11:38:30 -0800
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I've been looking at ideas for electrically raising and lowering a 
vertical antenna (like a 6BTV or R7000 style... basically 20-30 ft of 
aluminum tubing).  One idea is to use a garage door opener (or a 
similar chain/track or leadscrew arrangement from some other source, 
but a garage door opener is probably the cheapest way to get a 8 foot 
long linear drive, 1/2 HP motor, etc.).

The other way would be to find some inexpensive gear box that runs 
at, say, 1 RPM (it would take 15 seconds to go 90 degrees) and has 
the torque capability to handle the wind load on a 30 ft mast. Any 
ideas on consumer products with this sort of capability (I don't 
think electric window drives are quite in the ballpark, but maybe?)

The moment load is about 700 ft lb for a 30 foot, 2" diameter mast in 
a 60 mi/hr wind. I suspect you could get away with a lot less as the 
drive, accepting the fact that the drive might slip if you try and 
actuate during a windstorm.  You could have mechanical stops to take 
the load once all the way up.  Of course, some drives (worm gear 
window motors come to mind) can't backdrive, and will break if 
overloaded on the output shaft.

700 ft lb @ 1 RPM is a pretty small mechanical load (550 ft lb/sec is 
1 HP, so we're down in the 1/5th  of  HP or smaller... a pretty small 
motor, with suitable gearing..  on 12V, something like 10-15 Amps.. a 
couple amps for a 110V motor).  probably a bit much for an 
inexpensive TV antenna rotator..

The overall idea is to hide a vertical antenna on a rooftop by laying 
it down when not in use.


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