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Re: [TowerTalk] VNA

To: towertalk@contesting.com
Subject: Re: [TowerTalk] VNA
From: Wes Stewart <wes_n7ws@triconet.org>
Date: Tue, 31 Oct 2017 05:24:40 -0700
List-post: <mailto:towertalk@contesting.com>
I second Jim's remarks about the VNWA 3E (and Dan's, AC6LA, software).  I use mine in the field with a 10" touch screen tablet computer (Motion) running, uck, Windows 10.  Not quite as friendly as a laptop but much more rugged.  If need be, I can save measurement data in a file and transfer it to the desk computer via Wi-Fi for additional analysis.

I have a couple of 50KW BC stations nearby that I've measured at -3dBm on my inverted-l.  As long as I start a sweep at 1.7 MHz or above I have no issue with them.

Wes  N7WS


On 10/30/2017 8:08 PM, Jim Brown wrote:
For about four years, I've been using the VNWA 3e, designed by German EE prof DG8SAQ and built by some hams in the UK under the name SDR-Kits. It's not a kit, it's fully built and tested. I paid about $770 then, delivered to my door, with calibration loads and a carrying case; thanks to Brexit, it's about $100 less today. It's quite well supported both by SDR Kits and by DG8SAQ via an email reflector.  In addition to the standard VNA functions, it does excellent TDR by taking the inverse FFT of a wide sweep. The unit has full spec to 500 MHz, and reduced dynamic range to 1.3 GHz.

The file export functions work well, there are built-in math functions that can, for example, transform an SWR sweep to 75 ohms. The unit is also supported by AC6LA's excellent Excel spreadsheets. SimSmith and most of AC6LA's spreadsheets are freeware. I regularly use his ZPlots to compute the fundamental parameters of coax by importing S11 data from the VNWA into ZPlots.

I regularly make Z measurements of antennas in the shack, measure the line with TDR to find its length, and export the data to SimSmith to transform the measurement to the antenna's feedpoint. I also use TDR to look for any problems along a transmission line. The unit stores multiple calibration files, so once you've done a calibration for one measurement setup, you can recall it on another day without the need to redo the calibration. The measurements in this report were done with the VNWA 3e.

http://k9yc.com/BandpassFilterSurvey.pdf

So were these measurements of DX Engineering's excellent NCC-1 phasing unit.

http://k9yc.com/VE3DO.pdf

73, Jim K9YC

On 10/30/2017 5:29 PM, Neal Sulmeyer wrote:
​My MFJ 259B is 25 years old and obsolete. Time for an upgrade.  I'm considering the AIM 4300 (updgrade to the AIM4170 recommended by ON4UN).

I would like to hear some opinions on this device and others from my fellow

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