On 6/2/2012 3:45 PM, Dirk Hacker wrote:
> Hello all,
>
> Does anyone know of any mfg's of tubular towers for more temporary type use ?
> (incl. surplus)
At one time, some one made a crank up, tubular tower with a "dirt
base". IIRC it went to either 35 or 40 feet and was rated for a small
tribander. These things tend to be a wee bit flexible. It's likely that
someone on the list remembers them. It might have been Wilson as it was
around that time.
The base was just a 5 or 6' pipe with ears welded on the sides. Those
ears probably extended out 8 inches to a foot and appeared to be about 8
inches long.
As DOM can be purchased with 1/8th inch wall it would be feasible to
build such a thing. Structural steel tube also comes in schedule 40 or
80 and is considerably heavier. Each section needs to be keyed to
prevent rotation as well. IF OTOH you want to turn the whole thing it
gets a bit more complicated.
An extendible mast like you describe would need to be in 12 to 15'
sections. That means it'd need to be in 3, 15' sections or 4, 12' (My
preference would be no less than 15') to make 35 feet with a 5'
overlap. You could cut the overlap in half to get a total of 40 feet,
but with only two and a half feet of overlap the leverage would be
substantial in much of any wind. The mast could be hinged to the top
of the base. So you'd bore the hole, plumb and set the base. Back fill
using lots of water to make a soupy mud that will leave no voids. Give
it a few days to dry, put the mast in place, and hook it to the hinges
and crank it to vertical. NOTE this type of base does not work well in
sand or peat. It takes a clay or sand clay mix
To go beyond 40 feet these things (self supporting, tubular, and strong
enough to support more than a small tribander) get massive with
relatively long sections. Most I've seen were like a wet noodle in
windy conditions.
I had 30 feet of masting extending above the top of my 45G. At the top
of the tower was a TH-5 which is a relatively small tribander. 15 feet
up was a 7L C3i 6-meter Yagi on a boom just shy of 30 feet by 3 inches.
At the top of the mast was a 14' cross boom that had a 12L C3i 2-meter
yagi on each end (vertically polarized). Inboard were a pair of 11L C3i
440 yagis. In winds gusting 30 to 40 mph the antenna movement on that
cross boom was almost unbelievable. I still don't understand why those
antennas held together. It did destroy a TB-3 and a TB-4 in about 6
years (give or take)
Good Luck,
Roger (K8RI)
>
> I am looking for a light / tubular type of tower approx 35'-40' high
> ...perhaps can crank down (i.e "nest") to 12'-15'
> ...needs to be stronger/more robust than fiberglass poles or "push-up" poles
> (from Radio Shack, etc.)
>
> Looking for similar to MA-40 tubular tower but doesn't require concrete base
> (i.e. temporary install)
> I want to put small/medium size tri-bander& 6m antenna on it.
>
> I've heard of some army surplus "quick-deploy" towers...these seem extra heavy
> to move around& expensive (>$500.00)
>
> Thanks for your ideas and help.
> Regards,
>
> Dirk H.
> KE7WVZ
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