Christian,
That's quite interesting.
Having started on the path by using John's instructions to look at some cables here,
I'm now quite curious what else can be done with Fourier Transforms on the nanovna.
This may be the nudge I need to complete the Steven Smith book on Digital Signal Processing.
Perhaps in a couple months when the foul weather hits and I can't work outside.
Got about halfway through last year when I was down with a bad back, but will have to
re-read and take some good notes as there is a lot of information to digest.
The book is highly recommended, a relatively easy introduction to the nuts and bolts
of how this sort of thing gets coded. And legally available as a pdf:
My forum posts are usually not quite so grumpy as in that first reply to you.
In the future, will remember to have a cup of coffee before posting.
Jerry, KE7ER
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On Sat, Sep 26, 2020 at 04:02 AM, Christian Zietz wrote:
Perhaps as a postscript an explanation why this is not merely an "academic"
exercise but it has a practical application - at least to me. This is also how
I found the discrepancy in the first place.
I have some devices that are basically lines with tunable delay and
attenuation. I like to use time-domain transmission (i.e., S21 transformed)
measurements in band-pass impulse mode, because these allow me to see both the
delay and the average attenuation (over the frequency range chosen in the VNA)
at one glance. See the screenshot for an example. This is especially important
when tuning the lines because in that way I get an immediate feedback
regarding the parameters I'm changing. But, of course, this then requires the
magnitude of the impulse response to be free of systematic errors that merely
occur due to the IFFT and related signal processing.
I hope this explains why I wanted to fix this in the firmware.
