[TowerTalk] Tower Questions

[K7LXC]

In a message dated 98-05-12 10:08:20 EDT, n9tzl@juno.com writes:

> 1. Whether to use screw in anchors or regular cement anchors? If screw
>  anchors are used I would think they should be at least 6ft. long?
>  Sources?

     I'd recommend real concrete anchors. The screw-in anchor that Rohn has in
their catalog is rated at 2,500 pounds of holding power whereas the 3/16 EHS
guys have 4,000 pound breaking strength. There are seven categories of 'soil'
and each has its own (and different) strength rating. Too many variables with
screw-in types. 

>  2. What to use for a top? I do have a 25AG3 but at present I do not
>  understand the purpose/function of the pointy tops?

       The tapered top sections are really designed for mounting one VHF/UHF
omni antenna to it (a typical commercial scenario). It works fine for ham
installations too as a sleeve for mast. A 25G-sized load isn't necessarily a
prime candidate for a thrust bearing since rotators can typically handle the
vertical deadweight load by itself.

>  3. Should I use a thrust bearing?

         If you've got the tapered top section, use it and save the money for
the TB and flat top section. 

>  4. Why does Rohn always place the top guys 5ft. down from the top? Sure
>  seems like it would be better to have them closer to the top??
>  
     This (like other Rohn specs) is for commercial antenna installations. It
is so there is enough clearance at the top of the tower for an antenna mount
and antennas. You're correct - for ham installations, installing the guys at
the top of the tower is the preferred method although using either scenario
hasn't proven to be problem. 

Cheers,  Steve  K7LXC

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