[TowerTalk] Antenna/mast height above tower?

[jeremy-ca]

Depending upon the length of the mast and the arrays that are on it there is 
going to be some moderate to strong  imbalance that will kick the mast out 
at the bottom when releasing the rotator clamps. There are many methods of 
holding the mast but none entirely satisfactory especially for long term (as 
in having to order parts). Since I lean to 20-24' masts and lots of aluminum 
attached to them I use 2 thrust bearings. The lower one is mounted on a 
rotator plate in the usual location on 25G and the rotator is mounted about 
5-6' down in the top section. With 45G I mount the bearing 5' down and the 
rotator is mounted where it gives sufficient clearance to remove or upgrade.

Besides making a rotator swap a simple and quick job it allows for perfect 
centering of the mast in a Tailtwister as well as removing the side thrust 
in any rotator.

A few more bucks but it beats climbing to free up a binding rotator or 
thrust bearing.

Carl
KM1H

----- Original Message ----- 
From: "Phil Camera" <kb9cry at comcast.net>
To: <towertalk at contesting.com>
Sent: Monday, July 23, 2007 12:24 PM
Subject: [TowerTalk] Antenna/mast height above tower?


> Having just spent the weekend up and down all three of my towers (and I 
> hate climbing mast steps also), each tower has only one antenna up top.
>
> One antenna is a KT36XA and all are 1 foot above the top of the tower. 
> Then you need to make sure you have enough mast extending above the 
> antenna so that you have enough to attach the/any boom guys for the 
> antenna.
>
> I also like to place the rotator down about 5 feet or so inside the tower. 
> This lessens the moment load at the top of the tower and it also gives me 
> plenty of mast within the tower to attach to in case I need/when it 
> happens to remove the rotator.
>
> So plan in advance exactly how you will remove/swap out your rotator; this 
> preplanning will reap dividends in the future when/if you need to do that.
>
> Phil  KB9CRY
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