[time-nuts] DIY VNA design

Bob kb8tq kb8tq at n1k.org
Mon Aug 22 08:05:57 EDT 2016


If you really want to work out the delays through all of this
GPS "stuff" ahead of the RF -> PPS conversion, a VNA is about
the only good way to do it. 


> On Aug 21, 2016, at 6:59 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
>> On 21 Aug 2016 03:19, "Attila Kinali" <attila at kinali.ch> wrote:
>> Moin,
>> I stumbled over a new open hardware/source VNA design:
> http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html
>> Unlike other designs out there, this one is very well done and has very
>> little room for improvement, without increasing the price considerably.
> I am not convinced that this is time-nuts related,  although I am sure many
> time-nuts either have a VNA or would like one. Such a project needs its own
> forum.
> That said, I don't know why the author is using directional couplers.  A
> bridge is much wider bandwidth.  It is more lossy though.
> The software is I believe the tricky part. The VNWA software is very
> sophisticated, with a lot of useful features like it can design matching
> networks,   The software in the PNA-X is very sophisticated too, but in
> different ways.
> I don't know what the author uses, but Qt seems like best choice to me,
> which can be be built on OSX, Linux and Windows.
> For many measurements power levelling is not required, so that bit could be
> dispensed with.
> The author seems of the opinion that a lot of the hardware imperfections
> can be corrected in software. Thak is true, but the the residual errors
> that remain are a function of the quality of the hardware.
> Anyway,  it is an interesting project,  but personally if I were going to
> go to the effort of building a 2-port VNA, I would build one with 4
> receivers.
> Dave
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