My thoughts. Nothing herein is PE-approved.
Guying a short tower like this one when you have a two-story house available
seems like a bad idea. House bracket the tower at the top of the second story.
How thick is that concrete driveway? If you've got a good 6 inches of
thickness, in combination with a solid house bracket, I bet it will work just
fine with some mounting bolts sunk into the existing concrete. Your PE probably
won't sign off, though.
Forget about unguyed completely.
Grounding - if near the house, you should be able to tie into a perimeter
ground and sink one or two ground rods near the base [through the concrete, I
guess] and get a reasonable lightning ground.
I have used a lightly loaded 38 foot Rohn 25 tower house-bracketed at 20 feet
for many years. The base is the Rohn temporary base with three drive-rods. It's
been used to support as much as a TH-7 or an az-el satellite array. One other
point is that the antennas on this tower are well below the tree-line, so the
system is never exposed to full wind speeds. If the building inspector ever
asks, this tower is a "temporary" structure.
The only negative thing I have observed with a house-bracketed tower is the
transmission of vibrations into the house. My installation happens to be on the
end of the house where my daughter's bedroom is. She has complained about
rattling, banging and rotor vibrations, so I currently don't have anything up
there.
73,
Jim K1IR
To:
"towertalk" <towertalk@contesting.com>
Subject:
[TowerTalk] New project
From:
"Its from Onion" <aredandgold@msn.com>
Date:
Mon, 9 Jun 2008 12:20:32 -0500
List-post:
<towertalk@contesting.com">mailto:towertalk@contesting.com>
Ok guys, new project time.
Rohn 25 3-10 foot stalks with a 9 foot top section.
base is a concrete driveway. Next to 2 story house.
Antenna is a TA-53 14' long at 55 pounds.
Rotor is a Yaseu 450. (thinking too small)
Questions;
1. Should I attach to house or guy?
2. What is un-guyed height for 25?
3. Base plate Hilti bolted into driveway or cut driveway and dig hole.
4. Don't want 2 inch copper strap running across driveway. Alternate ground
ideas please.
The big question is grounding. If this was in a field I know what to do, but
since I'll be in the middle of a
driveway it's a tad different setup.
It would be nice with no guys, but also the same bolted to the driveway instead
of a 2x2 hole in it.
Thanks in advance.
Lee
KE4VYN
_______________________________________________
Jim Idelson K1IR
email k1ir at designet.com
web http://www.k1ir.com
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