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Re: [TowerTalk] LMR-400, damage?

Subject: Re: [TowerTalk] LMR-400, damage?
From: "Roger (K8RI)" <>
Date: Tue, 20 Jul 2010 17:11:30 -0400
List-post: <">>
Hi Steve,

There are many on here who do this for a profession and know more than 
I, but...
All cables are subject to lightning damage including those much larger 
than LMR-400 as well as multi conductor control cables.
As far as testing LMR-400 or any coax, there are a number of 
possibilities.  A Time Domain Reflectometer(sp?) or TDR, and antenna 
analyzers are two.  Undoubtedly there are others. The TDR which is of 
course the most expensive will even show you where in the coax the 
problem exists.
However if the coax were damaged you'd *likly* notice reduced 
performance in the system, or replacing the hardware would not have 
helped.  OTOH The jacket could be damaged allowing water to get into the 
shield and you'd never notice until corrosion had time to develop. So 
you also need to physically examine the coax for damage in addition to 
looking for electrical problems.


Roger (K8RI)

On 7/20/2010 4:43 PM, Steven McGehee wrote:
> Hello,
> I have a 150ft piece of Times Microwave LMR-400 in production with one
> end inside structure and the other connecting to a transceiver on a
> rooftop. We had some electrical storms come through in the past few
> days, and one evening we lost both the transceiver and the IDU (indoor
> unit) controller of said transceiver. Both were damaged and acting
> strangely, replacing just one of the two didn't work. To get the system
> functioning again we had to replace both the transceiver and the IDU.
> My question is, assuming the damage was caused by lighting (I haven't
> found any hard evidence to suggest it was, but, it seems to be the case,
> awfully coincidental otherwise) -- could/does LMR-400 "get damaged" by
> lightning? I feel like that's a very basic question, but I just want to
> be sure we don't need to replace that cable in addition to the two
> components we have replaced. Since the replacement work (two days),
> everything has been fine, but I didn't know if maybe, somehow, the
> internals of the LMR were potentially damaged too.
> On that note, is there anyway to test an LMR cable? In Ethernet
> scenarios I use a Fluke brand cable tester, is there a similar tool that
> can be used for "checking" LMR-400?
> Thanks.
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