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I have a nanovna that continues to indicate 50 ohms when S11 is open. Only if I short-circuit the input will this change. I already calibrated it. But this did not help. Can I do something about this or is it just damaged.

Did you apply RESET prior to CAL. Sounds like a faulty CAL.

Yes, I have also done a reset before calibration

Check all your cal loads to make sure they have the correct impedance.

Loads are good. When I calibrate my nanovna-f with it everything’s works perfect. Just to be sure I have measured them and they are correct.

I have a nanovna that continues to indicate 50 ohms when S11 is open. Only if
I short-circuit the input will this change. I already calibrated it. But this
did not help. Can I do something about this or is it just damaged

That very much smells like bad calibration, which I get far too often.
Watch Smith display during calibration.
It will generally be incorrect, but should change between open, short and load.

On Thu, Jan 9, 2020 at 11:16 PM, @ColinDexter wrote:

Loads are good. When I calibrate my nanovna-f with it everything’s works
perfect.

You can help people helping you by posting some picture.

Steps to take:
1: Go to calibration and do a reset and just to be sure switch the calibration off. (did you switch it on after doing your calibration???)
2: take a picture of the nanoVNA screen doing 0-900MHZ scan with nothing connected.
3: take a picture of the nanoVNA screen doing 0-900MHZ scan with the short connected to CH0. Do NOT use a cable but connect the short directly to the CH0 SMA
4: take a picture of the nanoVNA screen doing 0-900MHZ scan with the load connected Do NOT use a cable but connect the load directly to the CH0 SMA

This will provide evidence you nanoVNA correctly measures functional calibration loads.

If this all is correct you have to reread the documentation in the wiki describing how to do the calibration.

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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

It seems that the more often I calibrate, the worse it gets. It also no longer indicates a short circuit :-(
I have attached the picture ope, short and load

Colin,
These are with calibration active, can you go in the calibration menu and switch of the calibration so we can see the raw measurements?
This will help understand where the problem is

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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

On Fri, Jan 10, 2020 at 10:52 PM, @ColinDexter wrote:

It seems that the more often I calibrate, the worse it gets. It also no longer
indicates a short circuit :-(
I have attached the picture ope, short and load

Although this is not the version I made, I am happy to remind you that you can view the correct data by simply switching the blue curve to CH0. The picture shows that the clone manufacturer uses very old firmware, and it is strongly recommended that you update the firmware to the latest version.

hugen

I have also seen this. Bad calibration kit.
In my case the 50 ohm load did not connect well to the nut ring, which caused bad calibration.
Order a new one in good quality.

Best
Soren

Hi Hugen,

True, it was sold as an original with the latest software. I soon realized that this was unfortunately not entirely true :-(
This was before I discovered this forum and read that there were a lot of clones…

Thank you all for your response. I will, as Hugen advises, first try to update the software.

Colin,

What You see in blue on the screen is the CH1 Smith Chart and the value off 50 ohm is to best of my knowledge the input impedance of CH1. Switch to Channel 0 reflect and the marker will jump to the right sida showing infinity. I just tested that myself since I was curious of the 50 ohm on an open CH1. Calibration with SOL on CH0 will not affect what You see on CH1.
Regards/Torbjorn

50 ohm on CH1 means no input signal to CH1 as expected

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NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Quite right, whatever impedance but no signal in on CH1 will show 50 ohm. Thanks.
/Torbjorn

Sometimes the 'scale' function needs to be reset to 1:1.
Bob