Several things to consider:
1. the mil surplus poles have a poor strength to weight ratio even if
you solve the weak coupler problem. Laid up fiberglass tubing is the
way to go.
2. no matter the material, the wind load of the spider will be very
high, probably more than the tower can handle
3. perhaps a top loaded vertical design would work, but then how will
that interact with the C31XR's? There are several of these in various
antenna books.
4. if you can have pole supports far from the tower for the far end
support ropes than #3 might work with some coil loading
5. most reports of towers inside 4 squares aren't good, see the topband
reflector for some threads, detuning the tower is a must
6. perhaps a simpler tower plus reflector wire might be possible
7. a vertically polarized delta loop held off the tower at the top is
something else to consider, run some EZNEC models. I tried many models
for phasing two on a 89' crank up but it was a no go.
Check the antenna books and do some modeling, low angle gain on 80m is
not easy,
Grant KZ1W
On 12/26/2015 19:29 PM, Hans Hammarquist via TowerTalk wrote:
Hi Tom,
The tube itself is pretty sturdy but the is a huge problem to connect them with
each other. They, at least the once I have, come with some silly collar that
makes it seems as they can be connected together. Yes, they connect together
but the collar does not have nearly the strength as the tube itself.
I think they were intended to be used as tent poles, not too many connected
together, maybe 3 - 5 pieces tops, and placed vertically.
I have no experience with the tubes shattering but I have had several collars
breaking. I once, and only once, manage to raise a 40 foot pole consisting of
these tubes. It was at two places attached guy ropes and a falling derrick
approach. (If I remember it right I used 13 tubes at the time.) Next time I
tried, I wasn't successful.
I doubt that you can use them for a long, vertical member unless you find a way to "weld" them
together. I guess a better approach is to "bit the bullet" and buy one of the "more
established' fiberglass poles.
Let us know your approach.
Best 73 and good luck de,
Hans - N2JFS
-----Original Message-----
From: Tom_N2SR via TowerTalk <towertalk@contesting.com>
To: towertalk <towertalk@contesting.com>
Sent: Sat, Dec 26, 2015 4:26 pm
Subject: [TowerTalk] those 4 foot 1.5" fiberglass army surplus tubes...
You see them all over the place: ebay, even Dayton. I'm looking to try and use several/many of them to create a horizontal "outrigger" or "boom" to keep an eventual 80m 4 square away from a C31XR that is at 40 feet. Unfortunately, that out rigger needs to be over 50 feet feet long, in order to clear the C31XR. There will be two of them, hence 4 directions. I know that I will have to create a boom truss to support it and the weight of the wire verticals, the coax and balun. The question is, is there a better way? I've looked at DX Engineering's fiberglass tubing. I've looked at Max Gain Systems (?) fiberglass tubing. I know that Vibroplex sells Spiderbeam fiberglass poles. Everything I look at seems to be for use in the vertical plane, not horizontal. So, any ideas? If I use those 4 foot surplus tubes, how to connect them together - permanently? I was thinking of epoxying them together and also use 2 stainless steel bolts in opposing directions. Will they
st
and up to UV or do I have to use Scotch 88 tape and protect them? My initial thoughts are to
mount a pulley at each end of the tube, and use that point as one of the connection points for the
"boom truss." I realize that I might even need multiple trusses along the
"boom" to support it. Thoughts? Other ideas? The tower is 90 feet, with a C31XR at 80
feet, so I can't just move the vertical up to clear the low antenna. The turning radius of a C31XR
is around 24 feet, so I don't have to go 32 feet out from the tower. Thanks.Tom,
N2SR______________________________________________________________________________________________TowerTalk
mailing listTowerTalk@contesting.comhttp://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|