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Hi QRP RX aka qrp.dds ?

The best way to check if the calibration done by stand alone NanoVNA using ideal calibration condition and by using a calibration by NanoVNA-saver is by sweeping a some 25cm long semirigid cable which has low loss and well defined Z0=50 ohm. For a male calibration the will be not much difference as the male calibration part are fretty good and the SMA female adaptor for Ch0 is already compensated in open condition by internal 50fF. It it still unclear why 50fF and for what. Maybe the designer also included the supplied male open adaptor. However I found that using nothing for open was looking like the right choice.

What you should see it a Smith chart trace from 50KHz to 900MHz following closely the circumference of the Smithchart and not running outside the circumference. I attach an image where I sweep a 20cm HP airline and with a semirigid cable I got the same fine result. Although it is done with the NanoVNWA-saver and using my HP85033C 3.5mm kit for calibration I get same result using the suppled male kit. This image proof the high quality of the NanoVNA and the best condition used for it investigation. The small bump extreme left is due to the 300MHz spikes when NanoVNA switches over to harmonic operation. OZ2M Bo has explained some time ago why the NanoVNA should not have gone beyond some 275MHz in fundamental mode, but "who in hell" measures around 300MHz ?.

The benefit of using my data is when you calibrate at the end of a test cable and want a calibration at the SMA male adaptors calibration plane, then you must use NanoVNA-user and enter the female data. When the sweeping a semirigid cable - now with a female adaptor at the end of the semirigid cable, (I have male and female in the two ends) you will see the trace is running outside the Smithchart if you have a female female adaptor with loss, because thee loss is embedded in the calibration (see attached image). If not then the trace will follow the circumference just like the male calibration did.
If you do not have a semirigid cable use a good quality short SMA test cable of some 220 to 30cm length and see it spins inward due to the loss in the cable. Select a S11 dB trace and observe the trace and note marker values for the two different calibration. For male calibration at Ch0 directly will show no difference I am sure but time will show what you experience for a female calibration.

Hope this is of help
You may show us your findings

Kind regards

Kurt

-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af QRP RX
Sendt: 11. oktober 2019 12:15
Til: [email protected]
Emne: Re: [nanovna-users] A way to improve the accuracy of the calibration of a male SMA connector



Hi Kurt,



yes, I just found your message.



Could you please clarify how I can check if cal-kit setting will help or not? What I should check after C0 change?