[TowerTalk] Hardline and temperature

[Roger Parsons]

I have some beverage antennas for 160m reception which
are fed through a long (>2000') length of 1/2" 75 Ohm
hardline. This is the older type with a solid copper
inner conductor - I believe that more recent hardline
uses a copper clad aluminium inner. There is a joint
roughly in the middle of the run which I made off
using a proper hardline connector which very firmly
grips both inner and outer conductors. I feed 24V DC
along the hardline and a separate 4 conductor armoured
cable for switching purposes.

When I was testing the system to get ready for the
wonderful DX which I hope will be on this season
[:-)], I found there was S9++++ noise on the system.
After lots of cursing the power company I eventually
got down to thinking and found that the outer
conductor on both sides of the joint had broken and
let water into the connector. The noise was the 24V DC
tracking across the wet dielectric of the cable.
Capillary action had carried water several feet up the
cable between dielectric and outer conductor. So I
fixed it all and the system is working fine again.

Now my question:

I presume that the failure occured because the inner
copper expands more than the outer aluminium and
something had to give. How can I stop this sort of
failure in future short of replacing all the line with
the newer type - which would be a lot of work and a
lot of money?

Any comments appreciated.

73 Roger
VE3ZI




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