[time-nuts] VNA design

Dr. David Kirkby drkirkby at gmail.com
Mon Jun 2 13:24:03 EDT 2014

On 2 Jun 2014 15:50, "Attila Kinali" <attila at kinali.ch> wrote:
> 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.

There are a few designs around.  The early version of the VNWA was
described in QEX. There is the N2PK design too. The latter has a limited
frequency range, but a high dynamic range.

All modern professional systems with two ports use 4 receivers.  Earlier
designs use 3 receivers which is not good for TRL calibration.

I think it would be a huge task. I think that the main issue would be the
I have been considering adding the "unknown thru" calibration method to my
HP 8720D. That in itself would be quite a task, but writing all the
software for a VNA would be a huge task.

I thought TAPR had a similar project but I don't recall it producing
anything close to workable.

BTW the software options for the HP 8753's are now easily available,  so if
you do buy an 8753 (probably the best choice), don't worry about what
software options it has.

I would really like to see an open hardware and software VNA,  but it would
be a lot of work.

If you do it, think about having 3 or 4 ports with independent sources for
optimal balanced measurements.

I don't think that there's much point producing a design with just a TR
test set.


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