Migration where the coax is laying on the ground is specific to several
types of coax where the materials for the center conductor and outer
(jacket, shield, and braid) have substantially different coefficients of
expansion, 9913 is one. I've never seen it in the LMR series with Al
inner and outer construction which OTOH is very poor about migration in
vertical runs. I've found LMR-600 to be very bad, but single turn
loops 16 to 18" in dia about every 50 feet or so, seem to cure it.
I used all, 9913 and was an advocate of proper weather proofing, until
lightening blew off all the weatherproofing and less than 15 minutes
later /I had water running out of the 2-meter rig.
Back then I used coax seal, or the 3M equivalent covered with 88 tape.
It not only removed all the weatherproofing, but the silver plating as
well, leaving the connectors looking like sand blasted brass. Blowing
dry air or N2 through it would have repaired it, but I gave all, or
almost all of it away.
73
Roger (K8RI)
On 6/5/2015 11:15 PM, Richard (Rick) Karlquist wrote:
On 6/5/2015 8:00 PM, Roger (K8RI) on TT wrote:
My experience shows "to me" that those using N-type connectors on
vertical runs without problems are quite lucky.
Coax with type N connectors is quite capable of center pin
migration in or out just laying on the ground. About
20 years ago, I bought a bunch of 43 foot long 9913 cables
with type N's at a swap meet. They came coiled up and I
just threw them in storage. By now, every single one of
them has the center pins sticking out both ends like
pinocchio. The ones that I used early on that got
straightened out for a while, but then were rolled up
did better.
I had some 500 foot runs of coax laying out on the ground
and over time, the center conductor migrated.
Going forward, I use PL259's exclusively to avoid this problem.
Except on my 7/8 inch coax.
Rick N6RK
--
73
Roger (K8RI)
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