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Re: [TowerTalk] 90 degree coax bend atop a crankup tower

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Subject: Re: [TowerTalk] 90 degree coax bend atop a crankup tower
From: Patrick Greenlee <patrick_g@windstream.net>
Date: Sat, 06 Jun 2015 09:43:05 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
At $22 each I'd just as soon Whip up a DIY solution.

First thing that comes to mind is a short length of galvanized steel tubing like EMT or similar, larger in ID than the OD of the coax. I'd drill a some holes in the tube in the bottom 1/4 of its length to accept some sheet metal screws and another hole say 3/8 of an inch from the end opposite the screws. This last hole is sized to take a length of wire with which the assembly is suspended (I'd size the hole to take 3-4 passes of the "seizing wire.")

With a grinder, file, or other means, dull (remover the sharp point) from the sheet metal screws so that when screwed into the aforementioned holes (don't have to be screwed in all the way) room is left for the coax. Tap the end with the screws with a hammer to make for a snug but not tight enough fit so as to deform the coax. Roughen the coax jacket for good traction (60-80 grit) where it will contact the potting compound. Insert the coax, adjust the screws so they are not deforming the coax. Pour in your catalyzed potting compound. You could use the polyester fiberglass type resin, or epoxy or the "Hobby Lobby" grape casting stuff...

Howzit work?

The potting compound grips the roughened coax jacket. The weight of the suspended coax pulls down on the coax inside the do-dad trying to pull the potting compound and coax out the bottom. The screws are in shear, resisting the downward motion of the potting compound. The ID of the EMT or whatever is less at the bottom of the do-dad than the top thanks to your hammer taps so any attempt at downward motion of the potting compound relative to the EMT results in radial compression of the potting compound making it grip the coax tighter for better traction.

This is a first cut at a cheap coax hanger. Please feel free to improve on it but please don't run the cost up a bunch.

If I could whip this out in 5 min off the top of my head then surely some of you smart guys could polish it up sufficiently to prep it for use. I think it should be doable for a couple bucks or so each. A few minutes of messing about with simple tools could make for a decent savings while making for a little shop fun.

No claim is made for having any beneficial effect on center conductor creep.

Patrick    N5G

On 6/5/2015 12:04 PM, Robert Harmon wrote:
Me again.
FWIW,  these are the cable strain relief grips I use.  One nice thing about 
these is you dont have to
rull the cable through to attach as you do with the braided ones.
These install right on the side of the cable easily and the sliding tapered 
clamp grips very well from the
weight of the cable.  I have been using them for years and no problems.
They are made by Hubbell I believe rather than Kellem.

http://www.amazon.com/GARVIN-CHOKR1-WEDGE-CLAMP-ACSR/dp/B007886EDO 
<http://www.amazon.com/GARVIN-CHOKR1-WEDGE-CLAMP-ACSR/dp/B007886EDO>

Bob
K6UJ



On Jun 5, 2015, at 8:43 AM, Robert Harmon <k6uj@pacbell.net> wrote:

I agree Rick.
I use the Kellems and they work great.
BTW,  I want order some more but I use the sliding clamp type not the braided 
ones.
Only see the braided ones now when I search on line.
They only make the braided ones now ?

Bob
K6UJ




On Jun 5, 2015, at 7:39 AM, Richard (Rick) Karlquist <richard@karlquist.com> 
wrote:



On 6/5/2015 7:20 AM, Patrick Greenlee wrote:
educe damage to the coax.
I haven't done/tried the following but solicit comments from those who
have:

Use a large radius of curvature 90 degree section of conduit to increase
the area of contact between the coax and conduit.  Use an adhesive
(spray adhesive sold for attaching auto trim or other good adhesive) to
why go to all this trouble when you can use a Kellems grip to hold
the coax?

Rick N6RK
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