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[TowerTalk] Reusing Coax

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Subject: [TowerTalk] Reusing Coax
From: "Roger (K8RI)" <>
Date: Fri, 10 Dec 2010 17:21:20 -0500
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I've had some SWR problems when using the DL5K above 20 meters and 
decided to try replacing all the 8X in the system with LMR-400UF.  I did 
have LMR-400 between the amp and AT5K.

As some may remember I had problems with LMR400UF  pigtails with some of 
it splitting, but I had a fair amount that appeared good. Each pigtail 
was 28' long so if any could be reused it was certainly worth saving. As 
most of the connectors were N type I had to remove them or use adapters, 
but wanting to use UHF connectors and also wanting to check the interior 
of the coax including shield, I decided to remove the connectors. All 
connectors were clean and the braid shiny so figured the rest in between 
had to be good so I proceeded to install UHF connectors and cut the 
cables to the appropriate lengths. I was into the third cable when on 
removing the jacket I discovered the braid was dull and contained a lot 
of white powder.  Even carefully inspecting the jacket I could find no 
splits or worn spots and this was essentially in the middle of a 28' 
piece. All the remaining "used" 400UF is now on the junk pile (a few 
with shiny connectors)  and I started over with some new 400 UF I had on 

I figure on saving the Davis BuryFlex(TM) for the new pigtails while 
using up the 400 and 600 UF either indoors or in conduit where it is 
protected from the elements.

Going back to my tower project and the chronology I figure the 400UF was 
installed in 2001 and 2002. It was removed around 2006, so it was only 
up there about 5 years. Not nearly as long as I had thought.

A couple years ago I discovered a piece of 9913 left over from when gave 
away and threw out about 1500 feet of the stuff .  I used it to feed one 
of the 40 meter sloping dipoles. One day the SWR started jumping around 
and the Alpha 76 was showing intermittent high reflected power.  My past 
experience with 9913 was hollering "WATER" loudly.  There was a splice 
in the cable just inside the 2" EMT inside the shop. I had to pull it 
back about 2 to 3 feet to get at the splice.  Even though it was indoors 
it was still tapped up.  When I peeled the tape off there were water 
droplets on the outside of the connectors.  When I disconnected the 9913 
from the LMR400 a stream of water ran out onto the floor. So, I pulled 
the cable back out through the junction box. let the antenna down, and 
removed the coax.  About 15 feet from the antenna end I discovered a 
hole that went through the jacket, braid, and into the dielectric. That 
let water run down the high side of the antenna  and 15 foot of coax 
before it could get inside the run down into the shop.

What put the hole in the coax? It might possibly have blown against the 
edge of the shop roof, but in retrospect that would have taken a pretty 
strong wind. Critters?  Bout the only thing that would be up there (at 
that angle) would be one of the large woodpeckers we have around here, 
but I can't imagine one hunting for bugs in the coax. OTOH they have 
tried to get bugs out of the vinyl siding and when they do that it's 
like being on the inside of a drum.

In one case the coax was bad. In the other the coax was a poor choice. I 
probably would have had the same problem with new 9913.  Just one more 
reason  why I no longer use 9913.


Roger (K8RI)

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