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Hi David
Sure we have has some discussion ? and also some very good one.
I wrote 1GHz because that is the nanoVNA environment. I have measured to 8GHz on a 4 channel R&S VNA with auto calibrator and the Fairview SMA open cap, which is just an empty cylinder like the one from Pasternak, barely showed anything but a fraction of a degree in phase difference
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af Dr. David Kirkby from Kirkby Microwave Ltd
Sendt: 11. september 2019 15:11
Til: [email protected]
Emne: Re: [nanovna-users] Calibration data statistics

On Wed, 11 Sep 2019 at 12:49, Kurt Poulsen <kurt@...> wrote:

Hi Reginald
Interesting approach but have you considered that the calibration kits
used then should be from the same supplier else you will have a spread
due to these are having different frequency characteristics and thus
add an uncertainty not justifying the nanoVNA hardware investigation
you are looking for. Just the short used can be with welded center pin
and other with turned disk/center pin, which will introduce a couple
of picosecond variation. Likewise for the open end cap there are many
versions I have at least 4 different models where the one form
Amphenol RF has a disk that close to the center conductor of the
female adaptor on the nanoVNA that it lead to high delays and even often create a short.

Kurt and I don’t always agree on calibration issues???, but in this case I agree with Kurt.

As I wrote yesterday. I had seen a paper where corrections were derived when calibrating 3.5 mm connectors with 2.92 mm calibration kits and visa versa. However corrections were not derived with SMA connectors due to the variability among them.

Other types have different mechanical structures, actually the best open is

nothing used for frequencies up to 1GHz.

I would be surprised if that’s not the case *well* beyond 1 GHz.

I plotted the data the other day up to 900 MHz, showing added the open supplied with my NanoVNA just increased the phase from the ideal 0 degrees, as it’s just adding unwanted capacitance.

The load will definitely have frequency dependencies where both the
resistance and inductive / capacitive component influence the
frequency characteristic. There will as well be deviation from sample
to sample and from brand to brand.

That’s why I select every load for calibration kits my company sells.
There’s too much variation among them

These comment not to kill your project but just to raise some concern
Kind regards Kurt

I am only about 70% sure of Reg’s aim. But if it what I think it is, then
I believe the variation among the SMA bits will make it a bit pointless
trying to collect the data I believes he wants.

Unless good quality N connectors are used, the same issues will arise. In
particular the shape of the male pin N is poorly defined.

Dave


Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

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