Beware of cheap underperforming clones

As of 2022 there are many badly performing clones on the market. V2/3GHz NanoVNA uses parts like ADF4350 and AD8342 which are costly and clones have been cutting costs by using salvaged or reject parts.

See official store and look for V2 Plus4/V2 Plus4 Pro versions only to avoid getting a bad clone. We have stopped selling V2.2 versions since October 2020, so all V2 hardware that are not Plus or Plus4 are not made by us and we can not guarantee performance.

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NanoVna-Saver - reference plane shift and feeding cable elimination help?

ok1vaw 2020/09/08 09:51

I am solving a similar problem. I have antennas with feeding cable of unknown length. I could not calibrate on the cable end of the antenna connection point, but they are quite low loss. On the other hand, I would like to see the correct impedance of the antenna on its connection point  to be able to match it.
I know that by use of TDR I am able to find discontinuity, so if I use frequency range, where the antenna does not resonate and MS11 is close to unity (for example it behaves like a short there in case of loop), I am able to find the peak length in the TDR. In the TDR window I have to give the type of the cable to have a correct velocity factor.
The only way, how to move simply the reference plane  is to use calibration menu and "Offset delay". The problem is, that offset delay could be entered only in picoseconds and TDR give the result in m, so you have to calculate it by use of speed of light and velocity factor.
Has anybody better idea, how to move reference plane directly to the cable end by use of TDR measurement?

mce66 2020/09/08 11:52

Hello,
maybe if you select the "Custom" cable in the TDR and insert a velocity factor of *3336* you will get the cable length in ps (even if TDR will still use the unit "m").
Just try...
Best Regards, Marco.

Kurt Poulsen 2020/09/08 21:45

Hi OK1vaw

Using the TDR function of with e.g. VF of 0.7 you find the length of you cable.

Then measure and save a s1p file for the frequency span of interest and then use ZPlots by AC6LA and import the s1p file and for same VF and length move the measurement towards the antenna. You must however know the cable type use and select it from the drop down list in ZPLots.

You will se it is not that bad a method 😊

Kind regards

Kurt



Fra: NanoVNAV2@groups.io <NanoVNAV2@groups.io> På vegne af ok1vaw
Sendt: 8. september 2020 18:51
Til: NanoVNAV2@groups.io
Emne: [nanovnav2] NanoVna-Saver - reference plane shift and feeding cable elimination help?



I am solving a similar problem. I have antennas with feeding cable of unknown length. I could not calibrate on the cable end of the antenna connection point, but they are quite low loss. On the other hand, I would like to see the correct impedance of the antenna on its connection point to be able to match it.
I know that by use of TDR I am able to find discontinuity, so if I use frequency range, where the antenna does not resonate and MS11 is close to unity (for example it behaves like a short there in case of loop), I am able to find the peak length in the TDR. In the TDR window I have to give the type of the cable to have a correct velocity factor.
The only way, how to move simply the reference plane is to use calibration menu and "Offset delay". The problem is, that offset delay could be entered only in picoseconds and TDR give the result in m, so you have to calculate it by use of speed of light and velocity factor.
Has anybody better idea, how to move reference plane directly to the cable end by use of TDR measurement?

Kurt Poulsen 2020/09/09 16:37

Hi

I have to correct myself 😊

Find first the cable to use in ZPlots and note the VF. Then use that VF for the TDR measurements

Kind regards

Kurt



Fra: NanoVNAV2@groups.io <NanoVNAV2@groups.io> På vegne af Kurt Poulsen
Sendt: 8. september 2020 21:46
Til: NanoVNAV2@groups.io
Emne: Re: [nanovnav2] NanoVna-Saver - reference plane shift and feeding cable elimination help?



Hi OK1vaw

Using the TDR function of with e.g. VF of 0.7 you find the length of you cable.

Then measure and save a s1p file for the frequency span of interest and then use ZPlots by AC6LA and import the s1p file and for same VF and length move the measurement towards the antenna. You must however know the cable type use and select it from the drop down list in ZPLots.

You will se it is not that bad a method 😊

Kind regards

Kurt



Fra: NanoVNAV2@groups.io <mailto:NanoVNAV2@groups.io> <NanoVNAV2@groups.io <mailto:NanoVNAV2@groups.io> > På vegne af ok1vaw
Sendt: 8. september 2020 18:51
Til: NanoVNAV2@groups.io <mailto:NanoVNAV2@groups.io>
Emne: [nanovnav2] NanoVna-Saver - reference plane shift and feeding cable elimination help?



I am solving a similar problem. I have antennas with feeding cable of unknown length. I could not calibrate on the cable end of the antenna connection point, but they are quite low loss. On the other hand, I would like to see the correct impedance of the antenna on its connection point to be able to match it.
I know that by use of TDR I am able to find discontinuity, so if I use frequency range, where the antenna does not resonate and MS11 is close to unity (for example it behaves like a short there in case of loop), I am able to find the peak length in the TDR. In the TDR window I have to give the type of the cable to have a correct velocity factor.
The only way, how to move simply the reference plane is to use calibration menu and "Offset delay". The problem is, that offset delay could be entered only in picoseconds and TDR give the result in m, so you have to calculate it by use of speed of light and velocity factor.
Has anybody better idea, how to move reference plane directly to the cable end by use of TDR measurement?

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