[TowerTalk] How to deal with Coax on a Crankup Tower

Mon Nov 19 11:58:14 EST 2012

Chris, KF7P makes arms with free sliding loops and also with hoops that 
the coax is tied to.

see http://www.kf7p.com/KF7P/CoaxArms.html

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.

Grant K71W

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
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Larry
> Loen
> Sent: Monday, November 19, 2012 7:22 AM
> To: towertalk at contesting.com
> 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
> was not.
>
> 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
> (I presume).
>
> 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
> purpose.
>
> 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
> it.
>
> 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?
>
>
>
> Larry Wo0Z
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