[TowerTalk] House Bracketing Rohn 25 or 45
aa4lr at arrl.net
Sun May 11 01:03:13 EDT 2003
On 4/22/03 7:18 AM, Eric Rosenberg at wd3q at erols.com wrote:
>Two questions re: house bracketing, something I've never done.
>I have a Force 12 C3SS, soon to be a C4SS, and am considering putting
>it up with their small WARC yagi.
For a bracketed installation, you may have to seriously limit the amount
of antenna you can place at the top.
>1. If I house bracket a tower (Rohn 25 or 45), how high can the tower
>and then the mast go above the roof line or top house bracket without
>guying, with one yagi or both?
Depends. 1) What is the maximum wind velocity for your county? 2) How
much antenna area do you place to place on the tower? 3) what kind of
tower (25 or 45)? 4) How high above the bracket?
I can give you an example. Where I live, the maximum wind is 75 mph. I
have an A3S ( < 5 sq feet of wind area ) on Rohn 25 about 24 feet above
the bracket, of which 19 is tower, and 5 feet 2" mast.
I could probably go as high as 7 sq feet.
Practically speaking, I doubt you could put two yagis on such a tower
without getting them terribly close.
Also, practically, you likely aren't going to put a yagi more than about
25-30 feet above the bracket, even with Rohn 45. For one thing, you've
got to climb the doggone stuff to install the antenna, and it get's awful
wobbly above the bracket.
>2. Where in the NEC is there a discussion of proximity of power lines
>(the drop to my house) and the tower.
Keep the tower away from the power lines. Too many hams die each year by
bringing antennas in close contact with power lines.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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