[time-nuts] VNA design

Attila Kinali attila at kinali.ch
Mon Jun 2 10:43:12 EDT 2014


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

The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin

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