[time-nuts] VNA design

[Scott McGrath]

Attila

You might want to look at the N2PK and DG8SAQ vector network analyzer projects there are also some commercial USB based 'personal' network analyzers out there starting about 6K 

As for directional couplers. I would suggest buying vs building Mini Circuits has a line of high quality inexpensive couplers in both coaxial and surface mount at price points affordable for individuals these really are a solved problem.   

You could of course build waveguide based Couplers at lower frequencies they would be physically large but easy to construct if you have access to machine tools

Most commercial VNAs are still in the boat anchor class for size and weight at the office we have a R&S 40 Ghz 4 port VNA and it's still huge and heavy along with a fleet of agilents

Sent from my iPad

> On Jun 2, 2014, at 10:43 AM, Attila Kinali <attila at kinali.ch> wrote:
> 
> 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
> 
> -- 
> 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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