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Re: [TowerTalk] Coax Losses on 160 and 75?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Coax Losses on 160 and 75?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 5 Aug 2016 23:24:17 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On Fri,8/5/2016 11:03 PM, Richard (Rick) Karlquist wrote:
No, this isn't the real deal.  A 2 port vector network analyzer
with full 2 port calibration is the real deal.  The wattmeter
approach has many error effects that are difficult to account
for.
Right. I've never considered using wattmeter(s) to measure loss in coax. 
Now I use a DG8SAQ-designed VNWA (vector network analyzer). Very good 
accuracy.
Before that, I used an HP generator as a source and an HP Spectrum 
Analyzer as an RF voltmeter. Using that for measurement, I could clearly 
see variation in the apparent loss below 2 MHz -- this was as a result 
of the mismatch between this coax (Zo of a real line is complex and 
varies with frequency) and the constant 50 ohm load and source 
terminations. BTW -- I was measuring a sample about 1,200 ft long.
73, Jim K9YC

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