[TowerTalk] 90 degree coax bend atop a crankup tower

[Peter Dougherty (W2IRT)]

OK, with so many recommendations, I'm going to go with Chris' product when
it comes time to replace the coax. Hopefully this year, but next at the
latest. I met Chris at Dayton and was very impressed by his fabrication
skills for the products he was showcasing. I ordered three Stainless Steel
dual clamps to connect 2" copper ground strap to my tower legs and found
them to be superbly constructed. I plan to put them into service shortly. I
have existing arms/rings already so it's just a question of replacing the
top arm with the sweep. Still trying to figure out the best way to guy the
coax, however.

For a 70' motorized crank-up does it make sense to have a bonding plate at
the top, given that (a) I usually drop the tower during stormy weather and
(b) My entire neighbourhood has 80-110' trees in every yard? I can
understand it for fixed length towers, that's for sure but I'm curious about
whether this is just adding complexity and line loss via more connectors,
etc, for an installation where it may or may not have any real benefit.


---------------------------------------------
Peter, W2IRT
www.facebook.com/W2IRT


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Steve
Jones
Sent: Thursday, June 04, 2015 12:39 PM
To: 'Peter Dougherty (W2IRT)'; towertalk at contesting.com
Subject: Re: [TowerTalk] 90 degree coax bend atop a crankup tower

Peter-

I had the same problem on my crank up tower.  I used a cable sweep made by
Chris KF7P, in Utah.  It is galvanized and mounts in place of the top cable
arm.

73,

Steve
N6SJ


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Peter
Dougherty (W2IRT)
Sent: Thursday, June 04, 2015 8:10 AM
To: towertalk at contesting.com
Subject: [TowerTalk] 90 degree coax bend atop a crankup tower

Hello all,
I’m using an old LM-470 crankup tower and have a question about best
practices in cable routing. At the moment I don’t have my coax feeds bonded
to the top of the tower. Feeds from all four antennas, after forming the
rotor loop, are taped securely to a cable arm. They make a sharp 90° bend
and then dangle by gravity through two more cable arms in their run to the
antenna switchbox mounted at the base of the tower. That 90 degree bend
cannot be good for the bundle of cables. It’s high-quality stuff that’s been
up there for 9 hot summers and 10 freezing winters now, and I’m thinking of
replacing it either this year or next, as money allows.

This picture shows how the cables are routed at present.
https://db.tt/Hd3R7rrI.

 

Is there a preferred method of routing cables that doesn’t involve a sharp
bend like that? I’m imagining there’s quite a nasty impedance bump going on
here, not to mention the potential for physical damage to the dielectric in
the heat and cold, etc. If I’m going to spend hundreds of dollars in new
feedline, plus the costs of having it installed (I cannot climb, myself), I
want to ensure it’s done to best engineering practices this time. I also
think having the lines bonded at the top of the tower would be a Good Thing,
as well, so maybe a way to incorporate that and a new sweep or something to
get the cables headed downwards more gently?

Thanks in advance. 


---------------------------------------------
GO FRC!
Peter, W2IRT


www.facebook.com/W2IRT

 

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