>I am of the religious persuasion of allowing the coax to freely slip
>through the coax standoffs while being secured only at the very top of
>the tower.
Me too. I found that this is the only method that works on the U.S. Tower
tubular series if you want to be able to raise and lower the tower remotely.
> I use Kellems #022-16-003 which fit cables from 0.35" to
>0.44", ideal for RG213-type cable. They are available at most large
>electrical supply outlets, although you may have to special order these
>smaller sizes.
At the moment, I'm using cable ties and tape, very carefully arranged to
avoid damage to the coax. I'd much rather use the Kellems grips, but until
now didn't have the correct model number. I wonder if someone like Champion
would be interested in stocking some of these? I'd certainly buy a couple.
How about it, Steve?
>By allowing the coax to slip though all of the lower supports, you will
>wind up with a large loose coil of cable at the base of the tower when
>it is lowered. The only caution here is that when you again raise the
>tower, you have to be careful the cable doesn't catch on anything at
>the base of the tower as it goes back up again.
Right! I raise and lower my tower remotely. The tower is behind a stand of
trees, so most of the year I can't see it. My first attempt at routing
cables resulted in a near-disaster when the coax snaggged. Luckily, the
antenna balun exploded and released the coax before any damage was done to
the tower. I have since made several modifications which, in my opinion,
prevent the possibility of snags: 1) Two extra standoffs added above and
below the motor housing (on the oppposite side) to keep coax from wandering
around the tower and getting snagged on the housing; 2) Replaced very stiff
LMR400UF with RG/213; 3) Built cage out of hardware cloth around base of
tower to prevent snags in area of base-mounted rotor; 4) standoffs mounted
at center of rotation (requires a cooperative rotor controller like the
DCU-1.)
After more than a year of successful use, I'd say the chances of a snag are
nil. The only problem is that the area around the base of the tower must be
kept free of snow. A couple of minutes with a shovel takes care of this.
When excess coax is laying on the ground in the winter, I check that it is
not frozen to the ground or underneath a sheet of ice or crusty snow before
raising the tower. Note that the tower can be lowered at any time without
checking snow conditions, so there's no delay if strong winds kick up. A
little extra precaution before raising the tower in the winter is a small
price to pay.
I'm planning on replacing the RG/213 with much less lossy 9913F. To my great
surprise, I found that 9913F is significantly more flexible than LMR400UF. I
would say it's about equal to RG/213 and perhaps even slightly more
flexible. Replacing that 80 feet of RG/213 will make a significant
difference on 10M, so it's well worth it.
>Some folks argue in favor of securing the cables at each support,
>because it prevents the large coil at the base of the tower. Instead,
>you wind up with a series of cable loops hanging from each support when
>the tower is lowered. Personally, I worry about the loops catching on
>the supports when the tower is raised and I also worry about the sharp
>bend radii when the secured cable is allowed to hang in its loops at
>each support.
I tried this on my tower and it's just not feasible. Even with the standoffs
staggered, there's just not enough cross section on a tubular tower to keep
the loops from twisting severely, which could result in a serious snag if
the coax does not untwist as the tower is raised. Also, there seemed to be a
virtually 100% probability that one of the loops would catch on a lower coax
arm or on one of the limit switches mounted externally on the top of the
fixed section. The old Wilson documentation recommends loops, but that was
for a manually cranked tower. I think even then you would have to have some
ropes attached to each loop to pull them away from possible snags (I know
one ham who uses this technique on a Tri-ex triangular crankup.) U.S. Tower
confirmed that loops should not be used on my tower.
73, Dick, WC1M
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