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Re: [TowerTalk] accuracy of antenna analyzers

To: "Tower Talk List" <>
Subject: Re: [TowerTalk] accuracy of antenna analyzers
From: "Jim Brown" <>
Reply-to: Jim Brown <>
Date: Fri, 10 Dec 2004 08:11:14 -0600
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On Thu, 9 Dec 2004 20:40:25 -0800, Jim Lux wrote:

>I've got the ARRL articles on measuring the VSWR measuring performance with
>calibrated mismatches, but I'm really interested in how accurately these
>devices measure the reactive component.

I have spent a fair number of hours with a CIA-HF, borrowed from another ham, 
and own an MFJ-259B that I've calibrated per Tom Rauch's applications note.  
Tom says that the concepts of the two analyzers is similar. None of the 
of this class give you the sign of the reactance. Somewhere on the web I 
to find an excellent review by a ham who compared three or four of them to an 
accepted standard, a GR 1606 bridge. It might have been on one of the reflectors. It is worth chasing down. 

Some general impressions.  These are 10-20% analyzers. They essentially 
measure the magnitude and the phase angle, then compute the R and X 
components. The closer they are to 50 ohms (or 1:1 VSWR) , the better the 
accuracy. The CIA-HF will give you an reading up to 1K ohms. The MFJ quits 
around 400 or 500 ohms. I wouldn't put a lot of credence in the answer of 
either in 
that range. BUT -- I have measured a lot of ferrites using a CIA-HF in a 
disciplined manner to create graphs of their characteristics, and I get curves 
are consistent and believable in the context of mfr data.   The CIA-HF will not 
display the smaller component, R or X, within 5 degrees of 0 or 90 degrees.  I 
view that as acknowledging the modest accuracy of the measurement.  MFJ may 
be doing the same thing when they quite at 400-500 ohms. 

Jim Brown K9YC


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