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[TowerTalk] A bit more information on LMR-400UF

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Subject: [TowerTalk] A bit more information on LMR-400UF
From: "Roger (K8RI)" <>
Date: Wed, 04 Aug 2010 17:58:55 -0400
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I mentioned a while back about replacing the LMR-400UF pigtails  due to 
them failing.
I was thinking that I should be able to cut the bad spots out and make 
jumpers out of them, so last night I started doing a QA job on the 5 
cables that are about 15 to 20 feet long.

Although they show the signs of some UV damage, the surprising part was 
the pieces that were in the three turn coil that laid on the tower top 
plate. There were many spots worn flat from sliding on the galvanized 
surface and several pigtails had multiple spots that had worn through to 
the braid.  On the surface the braid did not appear to be corroded on 
several although it had dulled in color. On two others there appeared to 
be some corrosion where the braid was exposed.

The jacket had dulled but was still flexible, although it appeared to 
have lost some of the elasticity as it no longer slid on the braid which 
was an improvement. Whether it is still usable for indoor jumpers 
remains to be seen.  I'll find that out when I strip the ends back.

I was beginning to think I would use a piece of LMR-600UF as the pigtail 
for the 7L 6-meter Yagi, but the wear on the LMR-400UF has caused me to 
change my mind and stick with the Davis BuryFlex(TM) for the pigtails. I 
do think the UF versions could be used on a smooth surface, but I doubt 
they'd be good much past 10 years based on the 5 year deterioration that 
I see from my installation

BTW I had given one piece a double wrap of Scotch 33 tape in the coiled 
portion and saw no wear on the tape or on the jacket underneath. This is 
one of the pieces that was originally damaged when the brake on an 
HDR-300 failed to engage when the antenna was being swung and the wind 
caught it.  Although a length of the jacket was split, the "tape 
bandage" did it's job better than the exposed jacket on the good pieces.

I'll pass on what I find when I strip the ends back.  I'd like a LMR-600 
version for the pigtail, but it appears the smaller Davis BuryFex(TM) is 
the best for that application so far. That and the longest rotator 
loop/pigtail is only 28'.


Roger (K8RI)


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