Hi
I have the V2 plus 4 and absolutely love it.  Everything works fine until today that I can no longer calibrate with a cable attached to port 1(see attached screenshot) with and without PC connections. The unit still works in measurements  with stored calibration settings. I can still do both SOL and SQLT calibrations without cable in port 1. I have swapped different sets of calibration standards and cables to eliminate the fault. As soon as I attach a cable in port 1, it cannot calibrate and show crazy traces flying all over the screen. I have done lots of small signal LNA measurements but I always use both appropriate I/O attenuators with total attenuation at least the gain of the amplifier. So there is no question of me damaging it accidentally in amplifier measurements. It is getting frustrating, my first unit had a faulty touch screen and I hope this one last a little longer! Any thought?

Have you tried to reflash the firmware?
--
Dave VE3TLY

Hi
Check that you do not have a E-delay value (set to '0')

Hi
After some wild goose chase of the fault, I swapped all sets of calibration standards and cables from my SAA V2. The V2 plus 4 can be now calibrated with a cable on port1, phew!!  I hope it is the end of the issue. I have the group delay set to zero and the latest firmware. There is an "apply" option which I dont know what it does.
I have four sets of calibration standards and I ended up mixing them  over time which is not a good idea. The problem could be caused by one of the cables or calibration standards that I am not still sure.

Curiosity comments .
You stated that you have calibrated   "with cable" .
Assuming you are using coaxial cable ,
in theory - if  the end load is equal to characteristic impedance
it should be OK
BUT
If you use cable the calibration is no longer "of the device " but
device plus the cable .

Is it not ?

Purpose of calibration is to establish KNOWN
reference and adding external hardware ( cable)
may be OK - it depends on application.

End of sermon / rant  .

Hi
Yes I use the coaxial cables come with the NanoVNA.  In S11 measurement, the purpose of the SOL (short, open, ,load) calibration with the cable in port 1 is to move the "measurement plane"   and remove the effects ( reflected power, phase shift, insertion loss) of the cable.

The purpose of the through (T) calibration is to "subtract" the effects of the second cable  in port2 (if any). for S21 measurement.  Similarly if you have any SMA adapters or attenuations, the measurement planes of the DUT must be moved accordingly with the correct calibration procedure.  I am not sure I understand your question correctly.

Buonasera,
il display del Tuo strumento si comporta come questo mio?
Saluti

Sorry, I don't understand

Most probably, you have damaged VNA input by static discharge. There is some switch on the input, which is ESD prone. Look to the forum, this can happen and with a clever hands the IC can be replaced.

It is possible if the nanovna is connected to an external antenna. I have not done this.

Another possibility is that it can be damaged by power leaking from the soldering station described in this youtube channel:

https://youtu.be/me7xX5qId7c

In the my case, the issue has been resolved after swapping the set of calibration standards and the cables from the V2 plus4 by SAA V2. It could be intermittent electrical contact due to mechanical fault.

I would check the cables, they are prone to failure. I have replaced mine several times over the last year.They fail in the connectors and become unreliable with intermittent or fail straight up. Also, the center pin of the jacks on the unit  / tru adaptor wear out unless you have a port extender and even that needs to be replaced periodically. Remember, SMA connectors are not meant to be constantly disconnected and reconnected. I.M.H.O. the use of SMA connector in this application is a mistake.I wish they would offer the V2plus4 in a N connector version, it would be far more reliable.I am actually thinking of re-packaging the unit into a different case with permanent N connectors.

John

Thanks for reply John.
My issue is that when switched on I do not get the opening screen, Smith Chart. My opening screen is a copy of the first result I got when I first used the NVna. Nothing I can do changes this.
When I try to make another test, I get the same result, it always defaults to the first test I made. I also cannot delete any saved items. In addition, when I was able to try and check vswr, on several antennae, it always comes up with the same swr 6.7. I know the ant are good, all around 1.1 to 2.0.
Baz

Sent from Mail for Windows

From: John Cunliffe W7ZQ
Sent: 30 June 2022 12:30
To: NanoVNAV2@groups.io
Subject: Re: [nanovnav2] V2 Plus4 bizarre calibration issue with cable #nanovna-saver

I would check the cables, they are prone to failure. I have replaced mine several times over the last year.They fail in the connectors and become unreliable with intermittent or fail straight up. Also, the center pin of the jacks on the unit  / tru adaptor wear out unless you have a port extender and even that needs to be replaced periodically. Remember, SMA connectors are not meant to be constantly disconnected and reconnected. I.M.H.O. the use of SMA connector in this application is a mistake.I wish they would offer the V2plus4 in a N connector version, it would be far more reliable.I am actually thinking of re-packaging the unit into a different case with permanent N connectors.

John

at least use extender (socket saver) or put an sma to n adaptor on it
and let it sit there

saa2n is just a v2 with 4 inch and sma to n adaptors (secured with a
solder blob) so if it work in one series ... then it does in others

repackaging will work (or should) ... or just let the n adaptor
permanently on the unit (like its done in saa2n)

if somebody writes a fw for a 7 inch ... THEN its time for a bigger case ;-)

greetz sigi dg9bfc

Am 29.06.2022 um 14:13 schrieb John Cunliffe W7ZQ:

> I would check the cables, they are prone to failure. I have replaced
> mine several times over the last year.They fail in the connectors and
> become unreliable with intermittent or fail straight up. Also, the
> center pin of the jacks on the unit  / tru adaptor wear out unless you
> have a port extender and even that needs to be replaced periodically.
> Remember, SMA connectors are not meant to be constantly disconnected
> and reconnected. I.M.H.O. the use of SMA connector in this application
> is a mistake.I wish they would offer the V2plus4 in a N connector
> version, it would be far more reliable.I am actually thinking of
> re-packaging the unit into a different case with permanent N connectors.
>
> John
>

Yeah indeed. I use port extenders at all time to reduce wear and tear from day one because the V2 Plus 4 is not cheap. For Ham operators, it is better to use N connectors for antenna measurements indoor or out in the fields. SMA connectors works for me as they are cheap.  I frequently build and test RF experimental circuits with SMA connectors. So I purchase them in bulk.