[TowerTalk] Unconventional Tower Installation

[K7LXC@aol.com]

In a message dated 6/2/00 8:02:07 PM Pacific Daylight Time, n4kg@juno.com 
writes:

> What kind of engineer would space heavy guys on 78 ft 
>  of R45 at 22, 44, and 66 ft, leaving 12 ft unsupported?
>  This arrangement GUARANTEES that you will NOT
>  be able to utilize the tower to it's full ratings.

      Well, the windload and guywire drawings for 45G, 55G and 65G are for 
commercial installations where there is a mount at the top of the tower and 
the tower is typically loaded with a myriad of omnidirectional antennas and 
occasionally a dish or two. Having the top guywires 6-10 below the top of the 
tower insures that there is unobstructed room at the top of the tower for all 
these antennas. 

       Also take a look at the General Notes for these towers and you'll see 
that Rohn has already deducted 8.0 sq.ft. for a symmetrical commercial 
antenna mount at the top of the tower.

      Ham applications put different stresses on the tower and the guys 
should CERTAINLY be attached at the top of the tower. 
>  
>  If you only have one antenna on top, and it is not very big,
>  you are probably safe, but it is a very inefficient design.
>  
       Let's not mix up a commercial application and a ham application.

>  If you have a long mast and multiple antennas on top,
>  you will very likely have an excessive bending moment
>  on the unsupported tower, at / just above the top guy 
>  under high wind conditions.  

      I agree. 

Cheers,   Steve    K7LXC
Tower Tech

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