[TowerTalk] Rohn 25 guy radius oddness.. 80% vs 50%?

[n4kg@juno.com]

Ryan,

The 80% guy radius specification is designed to allow 
maximum loading on a tower at the rated maximum
height with a reasonable guy radius.
(For Rohn 25,  200 ft is the maximum rated height).

One of the design considerations is the maximum
vertical load on the bottom section.  For TALL towers
with a MAXIMUM antenna load, this is a major 
consideration.  

The closer the guy anchors are to the tower, the
greater the vertical load due to guy tension.  If guys
are moved in from the recommended 80% radius,
then the tower height and / or tower load must be
reduced.

For SHORT towers with SMALL Loads, vertical load
is not much of a consideration.  As Kurt Andress K7NV
aptly stated, "ANY guys are better than NO guys!"

Have you noticed how close the utility company guys
are on power poles?  Good example of a short support
with a small to moderate load.

I would not expect any problem with a 50% guy radius
for a 60 ft tower and SMALL antenna load.

de Tom  N4KG
......................

On Wed, 17 Nov 1999 20:06:47 -0800 (PST) Ryan Niemi - AV
<zippy@sunsetd.com> writes:
> 
> 
> Hi everyone,
> 	I've been browsing the TowerTalk reflector archives for a 
> while,
> to gather as much info as I can before installing a small Rohn 25 at 
> a
> hilltop site.  I just received my Rohn Consumer Products catalog
> yesterday, and ran across some interesting things.  Hopefully 
> someone has
> some insight:
> 
> 	I see Rohn usually specifies the guy radius for their towers 
> as
> 80% of the height.  But near the back of the catalog, they have some
> drawings for Rohn 25/45/55 for use with TVRO (?) dish antennas, and 
> show
> all of them with a 50% guy radius (with 3 way guying, even), with up 
> to a
> 6' dish at the top of the tower.  The drawings are in the Mounts 
> section,
> pages MS-62 through MS-67.  Any idea what's going on here?  I'm 
> looking at
> putting up anywhere between a 40' self-supporting tower and a 60' 
> guyed
> tower.  My site will be on a small piece of leased land at the top 
> of a
> local hill, with future lease rates depending on how much space I 
> take up,
> so I'd certainly like to look into why Rohn shows their towers with 
> 50%
> guy radius in some cases.  My antenna load will be very light, with 
> just a
> 17" whip at the top and a small parabolic grid at the 20' level.  
> What are
> TVRO antennas, and why does Rohn show their towers at a 50% guy 
> radius
> when used to support TVRO antennas?  I see the Rohn drawing 
> specifies this
> layout for a 70MPH basic wind speed, and I'm in a 75MPH zone.  Would 
> I be
> ill advised to consider setting up a 60' Rohn 25 this way?  I guess 
> I'd
> still be following the LXC directive if it's in the Rohn catalog, 
> but
> perhaps I missed something important somewhere.. (?)
> 
> Thanks,
>  -Ryan
> 
> 
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