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Old July 2nd 07, 02:02 PM posted to rec.radio.amateur.antenna
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Posts: 199
Default Rohn 25G without guys, how high?

On Sun, 01 Jul 2007 15:20:54 -0400, "Rick (W-A-one-R-K-T)"
wrote:

On Sun, 01 Jul 2007 16:58:42 +0000, Dave wrote:

sorry, think again... no hinge bases allowed on free standing towers.


Hmmm ... OK, I guess I will have to be able to climb it...

I suppose I could install temporary guys while I'm up on it doing antenna
work, but in that location permanent guying wouldn't work too well...

free standing towers must embed the base section in concrete.


How about the BPC25G base plate (non-hinged)?

I already have a concrete base in place, 6 feet deep, intended for the
predecessor to the US Tower MA-series crank-up mast. The mast (and the
base, and the tower on the other end of the house) belonged to my father
when he lived with us, but he sold the mast many years ago, and the new
ones are a bit too pricey for me right now.

So, it's too late to embed the bottom section directly into the concrete,
at least in that location.

I have the early model Crank up mast (Wilson, CT-77) that I brought
with me from Ohio in 1993. No one would give me $400 for it! The top
section failed (overloaded with VHF-UHF stuff in 1980's while in a
guyed configuration. It twisted and developed a diagonal crease.

Some time in the late 1990's I restored the mast and built a home brew
base for it. With the top section removed it is about 55 feet.

I had an opportunity to examine a factory built erection base and I
felt too many compromises were made to keep it shippable. I was able
to acquire scrap steel from a local salvage yard. I mounted a 1/2"
steel plate (actually 2 1/4" pieces) about 20" x 30" on wide spread
1/2" J-Bolts embedded in 5 Yards of concrete (5 yards is overkill, but
that was the minimum charge so I elected to use it). I think they were
about 36" long. I feel the J-Bolts are the weakest part of the design.

I mounted an I-Beam vertically (about 12 feet tall) to the plate with
1/2" Grade 8 bolts and heavy angle iron to the base. I also mounted
the hinge plate for the mast to the plate. Then I fashioned a pulley
arrangement from the upright to raise & lower the tower.

The tower at the 23 foot mark with a Cushcraft A3S beam and a G800
Yaesu rotor is load enough to raise and lower. In that configuration a
ladder is still needed to reach the beam mounting bolts due to the
length of the antenna elements and the boom length.

The combination seems to handle the weather better at about the 45
foot mark so I seldom raise it above that.

I use an electric boat winch to raise & lower the mast extent ion. I
have been using a crank winch to raise & lower the tubular assembly.
Hopefully, I will get that converted to an electric winch sometime
this year. Age is catching up with me.

We have Hurricanes & Ice in North Carolina. However, the wind rarely
exceeds 80 mph in my area. I expect to lose the antenna some day but I
doubt the tower will fail.

Although I had an electric welder available I used nuts & bolts
because I felt my welding skills were suspect. I had a small back hoe
(Terra Mite) available for the digging & Heavy lifting.

I would do it again. But I would not consider it with a non
retractable mast.

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"


 
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