[TowerTalk] Yum, yum! That LMR400UF sure is tasty!

[Dick Green]

Well, that's what the critters on my property seem to think...

After five months (yes *five* months) of continuous snow cover, El Nino has
graced the Upper Connecticut River Valley of New Hampshire with record warm
temperatures. In 27 years of living here, I've never seen it get up to 80
degrees in March! A week ago we had more than a foot of snow on the ground;
today it's almost all gone.

A casual trip down to the antenna farm during CQ WPX on Saturday revealed
that the animals went to town as soon as the snow pulled back from the three
100' lengths of Times Microwave LMR400UF coax running along the ground
between the antenna switch and the 40M vertical, 80M inverted vee, and old
GAP Titan. I found tiny teeth marks wherever the snow had melted, and in
several spots the coax jacket had been either flattened or bitten through to
expose the shield braid. Hard to say what kind of animals did it -- the
tooth marks were small enough to be from mice, but the flattened sections
must have been done by something bigger (maybe deer, which are plentiful
around here.) They even managed to gnaw on the coax and connector bootie at
the base of the GAP vertical, which is almost three feet off the ground.

It's kind of odd because they didn't touch the 20-50 feet of RG/213 that was
often coiled up on the ground at the base of the crankup tower and fully
exposed all winter long. I did see tooth marks on a small section of the #16
three-wire outdoor AC (!) line running between the pedestal and the tower
motor. It's almost four feet off the ground.

I got to wondering about the composition of the cable jackets and how much
that may be contributing to the problem. For several years, the GAP Titan
had a section of yellow-jacketed mini coax laying on the ground. Once or
twice a year, the amp protection circuits would trip (always during a
contest) and I would go down to the antenna and find that the critters had
chewed through the mini coax again. I got so sick of fixing it (usually in
the rain or snow), that I finally added a flush-mounted SO-239 jack to the
antenna. What's strange is that there was at least six feet of exposed
Belden 9913 connected to the mini-coax and they never touched it. In fact,
last year when I installed a 250' conduit run between the house and antenna
farm, I pulled up 250 feet of 9913 from where I'd buried it six inches under
the grass three years earlier and found absolutely no external damage
whatsoever.

The jacket of the 9913 is hard and shiny. The jacket of the RG/213 is
softer, but it's kinda shiny too. Both the LMR400UF and the #16 AC wire have
soft, matte-finish jackets. I've also noticed that a fine white powder has
formed on the LMR400UF jacket (UV damage?) Does anybody know the composition
of these cable jackets? Any idea why the animals seem to prefer one over the
other? Are there any substances I can put on the coax to keep the critters
off? (Yes, I'm willing to relieve myself on the cables, but I'm afraid it
will take quite a few beers to cover 300'...) Conduit is not an option (not
after installing three expensive 250' runs last year). Direct burial is
possible but very difficult (all three runs pass through thick woods with
lots of exposed or shallow tree roots, and one run passes over a radial
field.)

73, Dick, WC1M



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