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Re: [TowerTalk] S21 to Rp & Cp - Equivalent Circuit

To: towertalk reflector <towertalk@contesting.com>
Subject: Re: [TowerTalk] S21 to Rp & Cp - Equivalent Circuit
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 12 Jan 2018 13:37:48 -0800
List-post: <mailto:towertalk@contesting.com>
On 1/12/2018 12:36 PM, Máximo EA1DDO_HK1H wrote:
I like to sit on the soil, or on the roof, and test the antenna. In that situations a self-capable VNA is needed and Anritsu is very reliable (high dynamic range and robust to in the band interference).

I understand that desire. Many of us own more than one analyzer for exactly that reason. My mechanical toolbox includes various sizes of screwdrivers, wrenches, cutting tools, a measuring tape, a micrometer, a small magnifier, soldering irons with two sizes of tips, and so on. My test equipment includes a dual trace scope, two instrumentation-grade RF spectrum analyzers, three instrumentation-grade audio analyzers, a mechanical movement VOM, two DVMs, four HP signal generators, a P3 spectrum display, three low cost SDRs that I can also use as spectrum analyzers, an MFJ-259B, and a couple of ancient AEA analyzers, one for HF, the other for VHF/UHF. Most of this gear was purchased used. It would be NICE to be able to use the same analyzer you can drag up to the roof for bench measurement of components. Not every problem can be solved with a hammer.:)

My initial measurement of ferrite chokes used an HP generator and an HP spectrum analyzer, with point-by-point measurements transferred to a Quattro Pro spreadsheet. They were the tools I had available. That worked, but it took an hour or so to measure one part an manually enter the data in QPW. With the VNWA, I can make a 30-60 second sweep and immediately see plots of Z mag, Rs, and Xs vs either log or linear frequency. Another minute or two is needed to save the S21 data in Touchstone format and save a screen grab.

BTW -- several VNWA users are running their unit on a Windows-based tablet. The VNWA is powered from the same USB port used for control and exchange of data.

73, Jim K9YC

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