Hi, gang,
I will soon be installing a Rohn BX64 in my back yard. To beef up the end
result, I plan to install only 6 of the 8 sections, leaving me with what is
hopefully a much beefier 48-foot tower. According to what I've read, the full
64-footer is only rated for 6 sq feet of antenna at 70 MPH (with a 10-foot
boom). I live in an 80-MPH max zone, and although I've never seen a Rohn
lattice tower fail with only a TV antenna on it in these parts, I'd like a
little more margin and a little more antenna. Minus the two top sections, the
wind load seems to be upwards of 20 square feet (way more than the 8-12 I
need), and I'm guessing that a 12-foot boom would also work. The tower will
hold up one leg of a wire horizontal loop and will host a rotator and a smaller
beam (a Tennadyne T-6, a Spiderbeam, a 2-el quad, a hexbeam, a friend's
mothballed Mosley Classic 33, or a multiband rotatable dipole -- only one at a
time!) VHF antennas will be on a different tower.
I have a few questions (naturally :)
1. I will need to purchase or fabricate a top plate and a rotator shelf for
what I think is "section 3" (top two sections of the BX64 are not installed). I
was planning to fabricate a triangular plate with three bent "mounting tabs"
that I can bolt to the three corrugated legs of the now-top section (two bolt
holes exist at the top of each leg). I was planning to use 3/16 steel plate (or
something similar), but I'm open to suggestion. I think Rohn makes such a
plate, but I'm not sure what it's called or what it costs (budget isn't
extreme). Suggestions?
2. I'm looking to add some kind of a thrust bearing to this top plate to save
wear and tear on my rotator (a rebuilt Ham xxx, Yaesu 450 / 800, etc). I'm
hoping to use "farm store / farm equipment parts," and don't want to spend a
billion dollars on Rohn's bearing. (Not looking to install massive
antennas...just want a solid, trouble-free installation cuz it's cold in MN and
tower climbing is sometimes impossible.)
3. I'm considering buying new bolts for the tower, and I've read up on the
dangers of using SS hardware, hardware of unknown parentage, etc. I'm okay
using Rohn "shouldered" bolts, but so far the least expensive package I've
found is about $150. It sucks when the bolt kit costs as much as the entire
tower...! Most of the existing bolts are in good shape, but some were
horrendously tight, and when we took the tower down we had to use a huge
breaker bar to remove some of the large-size bolts. I'm not especially keen on
reusing those... Any secret sources for reasonably priced BX bolt kits?
4. I haven't looked at the catalog specs in a long while, but I installed many
BX48s back in the late '70s. I think a lot of installers back then (perhaps
today, too) dug holes that were too small. Still, none I've ever seen fell
over, except when matched against a tornado. I was planning to dig a 4 x 4 hole
5 feet deep, lined with golf-ball size rock for drainage and probably with a
minimal rebar cage and Rohn stubs. My soil type is very sandy, but well-packed
(new to me). I haven't checked with the utility company yet to see if they have
a psi rating for the soil in my part of town. The two companies that install TV
towers in this area don't do anything differently regardless of soil types
(naturally!). And I think their holes are too small, anyway... Thoughts?
Thanks, gang, I appreciate your input,
--Kirk, NT0Z My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
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