[CQ-Contest] [TowerTalk] Rohn 25 bracketed at 15'

[Dave Hachadorian]

It looks like Gorham, ME is in the 80+ wind zone.
At 80 mph, no ice, the Rohn catalog says 11.3 sq ft max of 
antenna centered at 10' above the top bracket. If you go 20' 
above the bracket, the allowable windload is about 5 sq ft, 
but that configuration will not survive 90 mph.

Dave Hachadorian, K6LL
Yuma, AZ


----- Original Message ----- 
From: "Alan NV8A" <nv8a at att.net>
To: "towertalk reflector" <towertalk at contesting.com>
Cc: "NY1E" <dickny1e at yahoo.com>
Sent: Tuesday, November 28, 2006 12:56 PM
Subject: Re: [TowerTalk] Rohn 25 bracketed at 15'


> On 11/27/06 07:13 pm NY1E wrote:
>
>> I am putting up a Rohn 25 tower with a house bracket
>> at 15'. The windload will be 11 sq ft, A3, 6M beam and
>> VHF vertical. I've heard some say you can go 35' above
>> the bracket, but that sounds like alot. I'd like to
>> get 40' up, 25 above the bracket, does that sound
>> reasonable???
>
> I have the 2004 Rohn catalog in PDF form, but I can't 
> remember where I
> found it.
>
> Page 107 has a table for bracketed 25G. For a height of 
> 40ft it shows
> *two* brackets, one at 15', the other at 30'. This is 
> claimed to support
> 11.3 sq.ft. @ 80mph with no ice.
>
> (For a height of 100ft it shows an upper bracket at 66' --  
> there's your
> "35' above the bracket" figure [close enough, anyway] --  
> but the
> permitted antenna area is a mere 1.7 sq. ft. @ 70mph with 
> no ice.)
>
> And keep in mind that they undoubtedly expect the antenna 
> to be
> immediately at the top of the tower, not sticking out the 
> top on a mast
> several feet long.
>
> 73
>
> Alan NV8A
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