HDBX help

[Roger Grady]

>In a message dated 96-12-07 16:05:56 EST, you write:
>
>>I was wondering if you had any ideas on how a Rohn HDBX-40 could be extended
>>in
>>height to maybe 48ft? I would like to use mine as a top loaded vertical and
>a
>>little extra height would be welcome. It seems that Rohn used to sell
>>straight
>>sections, but no more.
>
>Hi, Chuck --
>
>    The Rohn BX series consists of eight 8-foot sections.  I'm not sure what
>an HDBX40 is since I thought all they marketed was the HDBX 48.  You should
>have the Rohn catalog.  Then you could measure the sections and see which
>ones you have.  Then all you have to do is get the next smallest section and
>you'll be up to 48 feet.  The total wind loading depends on which sections
>you're using.  
>
>HDBX48    sections 8 thru 3   18 sq. ft. wind load capacity
>HBX56      sections 8 thru 2    10 sq. ft.
>BX64        sections 8 thru 1     6 sq. ft.

The rating of the BX series towers is determined by the size of the _top_ 
section. A HDBX has a #3 top section, a HBX has a #2, and a plain BX has a 
#1. Bigger top section = stronger tower & greater antenna load rating. 
That's why a HDBX can't be higher than 48'. A HDBX-40 is composed of 
sections 3-7, a HDBX-32 is 3-6.

I put up a used HDBX-40 several years ago. I wish now I hadn't been so 
frugal and had bought the #8 section for the bottom to push it up to 48'. I 
could go to 48' (or even 56') by putting #2 (and #1) top sections, but that 
would reduce the strength, and standing on those x-braces is murder on the 
feet on my #3 top section - I hate to think how bad even smaller ones would be.

Roger Grady  K9OPO


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