Hi Jerry,
Unfortunately, there is no easy way to put the rotator down in the tower exactly
where you would like to have it. You will discover that the standard Rohn
rotator shelf will only mount in a standard Rohn 25 tower in a space that has no
diagonal bracing. Such a space without diagonal bracing is located within about
two feet of the top of standard Rohn top sections. If you want the rotator
lower in the tower than that, you have to do something special to make it
happen:
1. Modify the tower by cutting out the diagonals. I would not do this without
being DARN SURE I was not compromising the strength of the tower too much. You
might need a Professional Engineer to give you the answer to this . . . I know I
would . . .
2. Modify the shelf by cutting away part of it so it will clear the
diagonals. Again, you need to be sure the shelf will still be strong enough
after you do this. I think this is less risky than #1 above.
3. Mount the shelf at the junction of the top section and the section just
below it where there is a short section of tower without diagonals.
4. When you get the shelf mounted where you want it, it is still tricky, but
possible, to get some models of rotators to fit inside the tower with the
diagonals still in place. Ham-M and Ham IV series will fit with some
encouragement and patience. Some models simply WON'T go in with diagonals
present . . . the Tailtwister, for example.
I have successfully used idea #3 above with the addition that I had to cut out
one of the bottom HORIZONTAL braces from the top section to get a Tailtwister in
and out of the tower. I have been using two towers modified in this way
successfully since 1973.
Stan
w7ni@easystreet.com
JerryC wrote:
> I am almost ready to put up my little 40' guyed tower. Everything is here
> or on the
> ups truck. There is a lot of discussion on mast stress and material type
> but haven't
> seen anything on how far the rotor should be below the thrust bearing. I
> am using 2" o.d.
> x 3/16" wall sae 1026 tuning. It came from the steel supplier at 21'-6"
> long. I am mounting
> a 4 el 10M vee (elements are up on 45 degrees on each side of boom) circular
> polarized antenna
> 10' above the tower top. The rotor is a Yaesu G800SA. In the future I will
> probable remove
> the 4el 10M vee and install a 3 el tri-bander about three feet up and put a
> small vhf stack on top.
>
> How far down should the rotor be located in relation to the height of mast
> above the thrust bearing?
> I could use the whole mast but would rather minimize the weight. I want the
> rotor far enough down
> to minimize the side load on it. Any suggestions??
> Thanks
> JerryC
> jerryc@netscope.net
> no call yet (still working on the code)
>
> List Sponsor: Champion Radio Products - We'll be at the Dayton Hamvention
> with all of our safety equipment and other products. Stop by booth #559 and
> say hi.
> <A HREF="http://www.championradio.com";>www.ChampionRadio.com</A>
>
> -----
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List Sponsor: Champion Radio Products - We'll be at the Dayton Hamvention
with all of our safety equipment and other products. Stop by booth #559 and
say hi.
<A HREF="http://www.championradio.com";>www.ChampionRadio.com</A>
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
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