Topband: N2PK VNA

[Jim Brown]

On 2/24/2014 6:56 PM, George Dubovsky wrote:
> The N2PK design is a well-regarded piece of kit, and I built one about 4
> years ago. It compared very well with the HP 8753 VNA I had on my bench at
> work back before I retired. It has a very enthusiastic following worldwide,
> surprising for something that is only available as a fairly complicated DIY
> effort.

I've heard the same universally good things about it, but last not easy 
to acquire -- last I heard, you've got to build the board, buy the parts 
and build it. I tried to do so several years ago without success.

However -- by all means look at the VNWA designed by DG8SAQ, nicely 
built by a UK ham. $700 delivered to my mailbox with calibration kit. 
Does simultaneous S11 and S21. Full spec to 500 MHz, reduced dynamic 
range to 1.3 GHz. Software is by DG8SAQ, who is a prof at a German 
university, and the softwae is still being actively developed. One VERY 
nice feature is that it is powered from a USB port -- no need to drag 
120VAC for power. Runs quite adequately with my 10 year old T41 
Thinkpad. Also does TDR and works as a spectrum analyzer. Support is via 
a reasonably active email reflector, which DG8SAQ reads regularly. I've 
been using mine for nearly 2 years now and am quite pleased. I bought 
the carrying case, which was a mistake. You want the 3E with everything 
but the case.

http://sdr-kits.net/VNWA3_Description.html

If you know what you're doing, it's easy to make Z and TDR measurements 
of an antenna in the shack, find Vf of the transmission line at the 
frequency of interest, and send the Z measurement to SimSmith software 
(freeware by AE6TY) to transform the data to the antenna terminals, 
design matching networks, etc.

The VNWA 3E was about to get a glowing review in QST a few years ago, 
but the guy who sells the AIM products queered it by threatening a 
patent fight.

73, Jim K9YC