Re: [Repeater-Builder] Coax run

Wed, 13 Apr 2005 17:23:25 -0700

Dave VanHorn wrote:
At 06:38 PM 4/13/2005, Mathew Quaife wrote:
  
Don't use 9913 in any repeater setting.
    

Would be helpful to state reasons, rather than blunt assertions.
It's kind of like software, I don't want to see comments that tell me 
what the code is doing, I want to know WHY it's being done this way, 
and not some other way.

Maybe you are new to the list.  This topic has been discussed in detail (even just recently) and it has been shown time after time that the dissimilar metals (tined copper braid, over an aluminum foil) will eventually cause noise in a duplex environment.
Either find some RG142 or use hardline of some sort.
    

I've had RG-213 recommended to me, as well as hardlines.
The trend seems to be twoard double braid shields, and away from 
foil, and twoard stranded copper center conductors, and away from 
copper plated aluminum, which has problems if you nick the copper.

RG-213 is nothing more than RG-8, it's single braid.

RG-214 Mil Spec (and yes it has to be mil spec to insure silver plating) is a very good choice for repeater cabling, especially of the transmitter.
RG-400 or RG-142 are good choices for lower power or receiver connections.
LMR400 is not even a good choice.  This I can affirm
to very quickly.  The shortest route is what I took for my jumpers.
    

I checked with Joe Lanoue, the product manager at Times microwave, he 
says the following:


"On LMR the mechanism for the PIM is actually the contact between the
aluminum tape and the inside of the connector body into which it goes.

I disagree.  It's the tin braid over aluminum foil that is the problem.
The silver plated shield on TCOM and lack of aluminum tape inside the
connector body negate the situation. "

Could very well be. 

At least Times finally affirms there is a problem with LMR, something that I have claimed for a long time.
Search the archives for more on the subject.

Kevin Custer


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