Hello everybody!

I am facing a problem when measuring the S11 using a nanoVNA V2_2, as you can see in the attached figure, when I calibrate the VNA using the NanoVNA native calibration kit the S11 signal does not display the notch that indicates the antenna's resonant frequency. On the other hand, when disabling calibration in the device the signal displays notch as expected. Has anyone gone through something similar?

Is that the return loss curve or SWR curve?
It may just be the response of the test cable poorly matched load.
Does it flatten out when you attach a 50 ohm load (in both calibrated
and uncalibrated modes?) in place of the antenna (preferably a known
good 50ohm load instead of the one in the calibration kit, in case
it's bad)..
The images are too heavily compressed to see the frequency span, but
if you are measuring a simple WiFi dipole antenna then I've never
found them to look anything like the text books say.
cheers,
Mark

On Wed, Jul 3, 2024 at 3:00 PM Laps via groups.io
<lincoln.aps=gmail.com@groups.io> wrote:
>
> Hello everybody!
>
> I am facing a problem when measuring the S11 using a nanoVNA V2_2, as you can see in the attached figure, when I calibrate the VNA using the NanoVNA native calibration kit the S11 signal does not display the notch that indicates the antenna's resonant frequency. On the other hand, when disabling calibration in the device the signal displays notch as expected. Has anyone gone through something similar?
>



--
Regards,
Mark

How long is the cable leading to the antenna?

It's the return loss curve. The frequency span is 800 MHz, and the center frequency is 2.4 GHz. I will run a test with another 50-ohm load. Thanks for the answer.

About 4 inches.

Did you calibrate at the unit or the end or the cable? Try calibrating “normal” and then add port extensions and bring it back to the “open” position ( right side on the 50 ohm line)

That nulls out the cable

At the end of the cable. I will try to do that, thanks for the response.