Chris, KF7P makes arms with free sliding loops and also with hoops that
the coax is tied to.
The hoop design keeps the coax from kinking, keeps it on the tower,
although enough slack is needed to still have an "upward" exit loop for
when the tower is fully extended. I'd guess about 5' more coax is
needed for every hoop vs loop standoff, if that loss is a concern.
My cable bundle per tower (2x HDX589) was 3 x 9913F7 or Buryflex (much
better stuff than 9913) plus rotator plus ethernet plus a 4 conductor
control cable for tower mounted gadgets. The hoop design worked fine on
one tower, but it wasn't easy for me to get the loops the right length
between hoops. On the other tower, they just wouldn't work - kept
getting snagged going up. Bundled cables seem to get a mind of their
own about twist and residual bends. Mine were carefully pulled without
any twist, then 3M taped every 18" or so. One tower's bundle was well
behaved on the hoops, the other wasn't. One of the rotator cables was
noticeably stiffer and with different coax that made the difference, I
think. Another risk with hoops might be trying to lower the tower when
the wind is blowing the coax around and it snags.
Steve K7LXC took one look at the hoops and said "that's not going to
work." Oh well, many trials with hoops had me talking to Chris and he
made it right by exchanging the hoops for loops and they work great on
both towers. I measured the offsets and extensions for the 589 as he
had not made them for that tower in its current UST revision. Now they
are a thing of beauty :-) .
Pre twisting the bundle is an interesting idea to keep it in a
container. I chose to use the mariners trick to flake heavy lines into
a figure 8 as the tower descends. Each half twist reverses the prior
half twist. One tower's concrete base grew large enough (another story)
that the coax flakes on it and the other is surrounded by grass so it's
not messy. Having a clean work area around the base is a really good
idea - gravel, grass, pavers, etc. It is small cost/effort considering
what is otherwise invested. Of course, I need to attend 100% the tower
lowering, but I wouldn't ever think of lowering these towers remotely.
On 11/19/2012 7:36 AM, Dick Dievendorff wrote:
At my last installations I chose option 1), and as I lowered the tower, I
guided the coax bundle into a circle on the ground. I added an angular
support to the topmost stand-off arm so that the weight of the whole bundle
was better supported. I had 6 RG-213 coax cables, rotator, and a control
line for 80/75 relays on a dipole. The coax bundle was taped together about
every two feet.
I saw a really neat installation at N6EK a few years back. Bob had a large
washtub inverted on the ground. He had applied the right twists to the
cable so that it coiled rather naturally around the washtub all by itself
when the tower was lowered.
73 de Dick, K6KR
From: TowerTalk [mailto:firstname.lastname@example.org] On Behalf Of Larry
Sent: Monday, November 19, 2012 7:22 AM
Subject: [TowerTalk] How to deal with Coax on a Crankup Tower
Slowly, but surely, my tower project is making progress.
Got a lot in place or will shortly finish. Tower is mounted, grounding in
place, A/C power. It's getting real.
Now it is time to consider a homely little problem I have given no
significant thought to: Routing the coax up and down the tower as I crank
it up and down.
The tower's manual gives me no explanation on the coax stand-off arms that
come with it. It states helpfully that when I install them correctly, they
will line up top to bottom. That was OK and expected. What is not obvious
is exactly how, exactly, the coax ought to "travel" on the tower.
The standoff arms themselves seem to consist of an open loop that has room
for several coax to be in them. Good as far as it goes. But, it seems to
admit to two designs.
1. Let the coax freely fall the whole 60 to 70 feet (this will vary based
on the three coaxes I will be running up the tower). The cable would be
"guided" by the standoffs, at least as far as the tower, proper goes.
2. Fasten, in some manner, the coax to each stand off. There would be a
modest amount of slack when the tower was fully extended and more when it
At the W0IBM club station, which had basically the same tower, the second
option was chosen. It would be using 9913 F for my runs, so that the coax
would be largely in the air. As at W0IBM, it would simply form a graceful
and natural loop between each standoff when the coax descended (I'm pretty
sure the W0IBM tower used RG8 or something flexible -- no 9913F back then).
I could also attach the DC control wires for the rotor to the coax as well
If I chose the first option, which the design of the stand offs kind of
superficially invites, the coax would have to "pool" at the bottom of the
tower, and it would do so in a place that looks rather unfriendly for the
It seems "obvious" to me that the second should be chosen, and yet I don't
remember seeing much discussion about this. Or, details about how to attach
Assuming the W0IBM solution is the right one (it would also help frustrate
the local copper thieves, too), how do I attach the coax to each stand off
and do so in a way that helps fight off the Arizona sun, which does things
like bleach "caution" tape in about a month's time?
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