[TowerTalk] Long feedlines

[Ian White G/GM3SEK]

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