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Hi all!
Is there anyone who can be so kind as to give me some help to make my device work again or at least tell me what has happened to my device?
I have a NanoVNA V2_2 - SAA-2N with the DiSlord firmware, version 1.0.69 - build time: Jul 31 2021 - 12:27:19.
The device has been working without problems for a long time, last time was yesterday or the day before. When I turned the device on today, I got a "strange" screen. I have always had a small point at the right in the smith-chart when input is open, a small point in the middle with 50ohm connected and a small point at the left, when shorted. Today I got something else! Please have a look at the pictures below. The open point is "big", 50ohm is smaller and short is still a small point. If I do a measurement, I get the correct "form", but the curve is not as "clear" line as I had earlier? I tried to load an older firmware, but the result is the same. I think there is a hardware error...
I will be very grateful for all the advice and views to solve the problem!

Karl Jan - LA3FY

On 21/09/2021 13:45, Karl Jan Skontorp wrote:

Hi all!
Is there anyone who can be so kind as to give me some help to make my device work again or at least tell me what has happened to my device?
I have a NanoVNA V2_2 - SAA-2N with the DiSlord firmware, version 1.0.69 - build time: Jul 31 2021 - 12:27:19.
The device has been working without problems for a long time, last time was yesterday or the day before. When I turned the device on today, I got a "strange" screen. I have always had a small point at the right in the smith-chart when input is open, a small point in the middle with 50ohm connected and a small point at the left, when shorted. Today I got something else! Please have a look at the pictures below. The open point is "big", 50ohm is smaller and short is still a small point. If I do a measurement, I get the correct "form", but the curve is not as "clear" line as I had earlier? I tried to load an older firmware, but the result is the same. I think there is a hardware error...
I will be very grateful for all the advice and views to solve the problem!
Karl Jan - LA3FY

Karl,

Cab you still calibrate the device. I wonder whether the calibration has been lost?

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Check your cal loads with an ohm meter to see if they are OK at DC.
Take a look at the inside socket of the SMA connectors. Perhaps "drilled out" by rotating pin after too may uses.

Roger

I have tried 3 different calibration sets, they all get the same result. Measuring at DC is ok. My NanoVNA is a SAA-2N, this is a device with N-connectors, so I don't think they have don their job...

Karl Jan

Yes, I can calibrate the device, but when doing measurements, I get a lot of lines in a mess. If you have a look at the photo - measurement - you can se a curve form, but rather thick. The form of the curve is correct, but there is a big difference between measuring point, and this makes the "thick line".

If time permits tomorrow, I will make a "correct measure ment with my NanoVNA-F and compare the result.

Karl Jan

I'm still struggling with my faulty nanoVNA SAA-2N :-( In addition to the SAA-2N I have got a nanoVNA-F, a nanoVNA-H4 and a small "very tiny...". The other units are working ok, but I really want to get my SAA-2N back in business! Today I tested the S21 measurements with the SAA-2N. I measured a 18MHz bandpass filter, and the unit seems to work ok in this mode :-)
The next thing I wanted to check was the level of the "output signal" on Port 0. I also have a handy spectrum analyzer, the tinySA. I put the SAA-2N in "CW mode" at a frequency of 8MHz. Connected the tinySA and observed a lot of harmonics, but the "main peak" was at about -23dBm!!! I think this level is too low! I did the same measurement on the H4 - result -8dBm and the nanoVNA-F had +3dBm. The result on the "very tiny..." was -7dBm.
When putting this together, I my first thought was the Si5351, but when I have done the rest of the measurements, I think one of the RF-switches, MXD8641, must be broken. Can someone please tell me if my assumptions correct?

Will be grateful for any response!

Karl Jan - LA3FY

Karl Jan,
My SAA-2N measures about -12dBm at 8MHz CW, but the signal pulses on and off during the sweep. (It is -12dBm during the on times, measured with an HP8563E SA.)
I am using the Ojisan version of the SAA-2 firmware.
--John Gord