[time-nuts] VNA design

[Collins, Graham]

There is a popular DIY VNA designed by N2PK, boards are available from a fellow in Ontario Canada, a quick google search should find the information for you.

Also, Sam Wettlerlin  has published much on his web site with respect to Scotty's Spectrum Analyzer project, VNA, return loss bridges, etc.

http://www.wetterlin.org/sam/

Also, there is an interesting project called the Poor Hams Scalar Network Analyzer (PHSNA) which may be of interest. There is an active Yahoo group. All that is missing is a phase detector to make it a simple VNA. Based on Arduino and the inexpensive AD9850/AD9851 DDS boards from Asia.

I'd like a VNA too but I am starting small with the PHSNA and will build from there. My needs are not that great, just as a learning tool and to support my ham radio tinkering.


Cheers, Graham ve3gtc




-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Attila Kinali
Sent: June-02-14 10:43 AM
To: time-nuts at febo.com
Subject: [time-nuts] VNA design

Hi,

I know this is not exactly a time-nut question, but i guess this is the best place i know to ask about this stuff.

I recently got introduced into the usefullness of a VNA. But these things are horribly expensive for home use, even if bought from ebay (before you say anything, remember i live in europe, where every boat anchor hast to travel a long way). But given that most of the designs that are on ebay are from the 80s and early 90s, i thought that with todays ICs it should be easy to come up with a design that does the same thing but can be build on a kitchen table.

Well, my problem now is, that i don't know how to build a VNA.
Yes, i understand the basic principle. I can come up with a design that should work. But i have no clue about any problems or difficulties in building these devices. Ie it's very likely that i fall into a dozen traps when i try to build one.

I tried to get information on how to build a VNA, or what kind of trouble people had operating one, but beside the VNA book[1] Rick mentioned a couple of months ago and ko4bb's site (thanks man! your manual collection is a gold mine!), my searches came out blank. As i'm quite sure that there is information of that kind out there, i would like to ask whether someone could point me to some documents, webpages, books, papers, etc that would show me the detailed design of VNA, the problems people had with some designs or anything else that would be of interest in such an endavor.


Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much appreciated. All papers i found deal mostly with stuff above 5GHz.
Seems like "low frequency" couplers are considered "a solved problem".


                        Attila Kinali

[1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques by Dunsmore, 2012

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