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Re: [TowerTalk] Coax Loss -- RG-Numbers Don't Tell us Much

To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Subject: Re: [TowerTalk] Coax Loss -- RG-Numbers Don't Tell us Much
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
Reply-to: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Fri, 05 Feb 2010 10:40:56 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Jim Brown wrote:

> Not as ideal as you might think. The problem is that most coax is 
> shipped on reels with access to only one end. To make a transmission 
> loss measurement, you must unreel it to get a connector on both 
> ends. 

No, see below

> 
> Now, if you happen to own instrumentation that allows you to measure 
> that loss on a 1,000 ft spool from only one end, that's another 
> story. :) 

See below

> 
> 73,
> 
> Jim K9YC

I happen to own instrumentation that allows me to measure loss from
one end; it's called an MFJ-259B.  Cable loss is a built in function.
As long as the far end is open, cable loss is half of return loss.
You can also calculate loss from VSWR.  For example, 3:1 means your
loss is 3 dB.

Rick N6RK
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