Rob Atkinson, K5UJ wrote:
>For the 2 or 3 hundred foot run out and up the tower, I'd definitely
>consider some kind of andrew heliax (not the stuff you have to
>pressurize),
In other words, foamed heliax with a solid copper sheath. The sheath is
firmly bonded to the foam, so water cannot creep along the inside.
The big advantage is not the low loss, but its ruggedness. It will shrug
off damage that would completely trash braided cable. It also lets you
make all kinds of "ugly" but effective repairs.
Damage to the outer jacket, it simply ignores - any water goes down the
outside of the solid copper where it can do no harm. This is a huge
advantage over braided cable, where a small nick in the jacket can suck
in water and ruin several yards of cable before you even know it's
there.
Most sizes of heliax are too big (or too obvious) to be seriously
damaged by anything like a mower blade. If you do slice open the topside
of the cable, exposing the foam, that still doesn't qualify as "serious
damage" - you can simply tape over it. You'd need to plane off something
approaching a half-wavelength before there is any serious signal
leakage, so patching with a soldering iron isn't usually necessary.
Heliax is also very easy to splice using hobby brass tubing for the
inner conductor, and split water pipe for the outer. Tape a wooden
stick on the outside, and your ugly splice will be even stronger than
the original cable.
--
73 from Ian G/GM3SEK
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