[TowerTalk] 90 degree coax bend atop a crankup tower

[Peter Dougherty (W2IRT)]

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. 


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GO FRC!
Peter, W2IRT


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