[TowerTalk] New Rohn catalog

[Eugene Jensen]

First, I have received the new Rohn catalogue and I have given it a quick
look, and I do think, Steve, that it will have some value as my recent
experience over the last few years have been in the Coastal regions of the
Eastern U.S. They are now requiring a massive wind speed which for most
practical purposes makes a crank up tower not to make the grade regardless
of the speck; it cannot hold up a light bulb at the coastal wind speeds.  I
think the real value of this is that if you are working on a coastal area
you are going to need a PE to design and sign off on a foundation and tower
for the plan load. Now Rohn provided me my basic tower drawings, and
foundation drawings signed off for South Carolina. They delivered me
completed foundation and tower load calculations. I installed an 80 foot
Rohn SSMW and for any of you that have the new catalogue, look at the top
four sections == those is what I have used.  As for the top of the tower, it
was necked down to 24 inch solid microwave Pirod and the structure was
designed by P.E. Hank Lunberg that will be the ring rotor supports. Though I
did not need signed plans for it, the county accepted his work and they just
considered it part of the antenna support assemblies. Anyone who is
expecting to put up a tower in a coastal wind area, I think you are going to
have to reconsider either a guyed tower or a very heavy self supporting
tower. Because FEMA has now told the States that they must use IBC 2003 and
as of this time it using the F calculation and I'm sure in it next revision
they will address the G rating. Also being an electrician by trade the new
NEC now has a whole section on tower and there grounding requirements. Horry
Country SC required the tower be grounded as per NEC.     

I also own UP The Tower and ANTENNA ZONING and I recommend that both be on
the bookshelf of any Ham who planning on installing or own a tower. 
73's Gene K2QWD 

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of K7LXC at aol.com
Sent: Monday, November 23, 2009 8:34 PM
To: towertalk at contesting.com
Subject: [TowerTalk] New Rohn catalog

Howdy, TowerTalkians --
 
    I picked up my new Rohn catalog from the mailbox  today and it's the 
whole catalog. I think what happened is that after  the first couple of
call, 
Stephanie started sending out the 25 and 45 sections  and not the  whole 
catalog. Other than that I've got no clue. 
 
    As far as the new catalog goes, I have mixed  feelings about it. It's 
slicker with a lot less engineering and specs and a lot  more white space on

the pages. It's more of a sales tool than hardcore  engineering handbook.  
 
    They're using the TIA-222 F AND G  revisions which IMO confuses things 
a bunch. The same tower will have two  different ratings for two different 
windspeeds and two different revs. I'm not  an engineer so am only 
peripherally familiar with the 222. Rohn spends a couple  of pages on Rev G
where they 
introduce new specs - structure class, exposure  rating and topographic 
category. Where in the past the old catalog had real  signed engineering 
drawings and some building departments accepted them, I think  anyone trying
to 
use these new ones will only confuse the building department -  I know it 
confused me. 
 
    Also there are no general engineering notes so  there's no mention of 
the 8.0 square feet of symmetrical mount that's deducted  from the net 
capacity in the older drawings but I think it's been added  back in.  
 
    I think there are lots of changes as far as the  specs go so be sure to 
check the CURRENT information. For example:
 
Old    45G 100'    70  MPH    22.2 square feet    guys: all  3/16"
New  45G  100'    70  MPH    24.3 square feet - Rev  F    guys: top - 1/4", 
bottom 3/16"  
New  #2    45G     90 MPH   17.0  square feet - Rev G    guys: top - 1/4", 
bottom  3/16" 
 
    So I think that the new Rohn catalog looks good but  now even more you 
need to get an engineer involved in your installation to get  the right 
specs translated to your requirements. And if you're going to  get a
building 
permit. 
 
Cheers,
Steve      K7LXC
TOWER TECH 
 
PS - I'm not an engineer so any additional clarification appreciated. 
_______________________________________________



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