>Roger: I've picked the TH7DX at 11.5 to compare (because I own two of
'em and two TH6's). This has, in the manual that came with my TH7, a
wind surface area of 9.4 s.f. If this is the number that one matches
with the Rohn 25G or 45G numbers in ovals or rectangles, then hams have
just lost 2.1 s.f. of loading. Or does the 11.5 now get reduced by some
factor? My question is: For a ham applying for a building permit, he
must produce an antenna number lower than the tower number -- so I hope
HyGain and Rohn s.f. numbers match. Could you comment for the reflector?
---------------------------
Fred,
The Rohn catalog that I have is dated July 1, 1987. It has a cover sheet
that references EIA-RS-222-C, which still refers to the wind zones A, B and
C. EIA /TIA - 222-E is quite different. It lists a basic wind speed for
each county in the US. (e.g. Lancaster County Nebraska is 80 mph)
The shape factors and formulas for calculating loads have also changed
quite a bit. Some of these formulas were in one of my posts to TowerTalk
on 5/29/98. I think that either Steve K7LXC or Kurt NI6W could give you a
better answer to your questions about current Rohn 25G and 45G spec's.
73 Roger WB0DGF
Telex Communications, Inc.
http://www.hy-gain.com
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