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I have an open circuit on the other end of some 50cm of coaxial cable. What is the easiest way to insert some delay to tune off that cable. NanoVna_save seems to need to calibrate the Vna after every delay. That is not very good because I don't know delay exact delay yet, I wish to test different delays until I see an "open" in charts.

Enter the delay in the calibration panel (negative number) the graphs will be updated realtime, no need for new sweep

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

Thank you. I did not notice it at first. There was a discussion about Vna_saver 0.21 which didn't look very interesting at first, but there was info about this. I should have read it first

I forgot the sign, + is surely not good. Is 1690ps good for a 32cm or one foot of coaxial?

On Sun, Jan 12, 2020 at 04:45 AM, Leif M wrote:

I forgot the sign, + is surely not good. Is 1690ps good for a 32cm or one foot of coaxial?
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For me the easiest way to determine a starting value for cable compensation is to use the TDR function of the NanoVNA (see attachment). It scales the x-values in units of time. The screenshot was taken using the latest version of Rune's excellent NanoVNA-saver application.

- Herb

On Sun, Jan 12, 2020 at 04:45 AM, Leif M wrote:

I forgot the sign, + is surely not good. Is 1690ps good for a 32cm or one foot
of coaxial?

There is a bug that in nanosaver. You have to multiply the delay by 10 and enter that into offest delay (under Calibration). So instead of 1690 you have to enter 16900 ps.

NanoVna_Saver shows only lenght, not delay.

On Sun, Jan 12, 2020 at 09:42 AM, Roger Need wrote:

There is a bug that in nanosaver. You have to multiply the delay by 10 and enter that into offest delay (under Calibration). So instead of 1690 you have to enter 16900 ps.
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Roger,
Try the version Rune released yesterday. That bug had been reported before and I believe Rune was going to fix it in the next release.

- Herb

On Sun, Jan 12, 2020 at 10:39 AM, hwalker wrote:

Try the version Rune released yesterday. That bug had been reported before
and I believe Rune was going to fix it in the next release.

- Herb

Herb,

Thanks for the correction to my previous post. You were right! The latest version has fixed the bug. I just made a number of tests using NanoVNA saver 2.2 with different length cables and got good results by just entering an estimate for one way delay and then varying for best results while watching the Smith Chart and S11 phase delay. .

I also compared using the offset delay in the program and the equivalent electrical delay parameter in the NanoVNA hardware and got agreement there as well. The electrical delay used in the hardware parameter is the round trip delay so I divided by 2 to get the offset delay in the Saver program.

Roger

On Sun, Jan 12, 2020 at 12:38 PM, Roger Need wrote:

" … The latest version has fixed the (offset delay) bug. I just made a number of tests using NanoVNA saver 2.2 with different length cables and got good results by just entering an estimate for one way delay and then varying for best results while watching the Smith Chart and S11 phase delay. .

I also compared using the offset delay in the program and the equivalent electrical delay parameter in the NanoVNA hardware and got agreement there as well. The electrical delay used in the hardware parameter is the round trip delay so I divided by 2 to get the offset delay in the Saver program. "
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Roger,
I'm sure Rune will be happy to hear those results. Kurt Poulsen had previously provided feedback to Rune that the "S21 phase delay has been fixed OK and the S21 group delay are still correct."

Kudo's to Rune for his usual excellence.

Crazy Houston and Chiefs game in progress.

- Herb

What about the TDR. There is no delay there.

I just checked and my NanoVna_saver TDR shows distance in meters.

On Mon, Jan 13, 2020 at 04:22 AM, Leif M wrote:

I just checked and my NanoVna_saver TDR shows distance in meters.
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Leif,
Check message #9483 in this thread. The math to convert from distance to time is probably trivial but not something I do frequently. You might put in a request to Rune to report the cable length in distance and time if pulling out a calculator is something you would rather avoid.

- Herb

On Mon, Jan 13, 2020 at 04:16 AM, Leif M wrote:

What about the TDR. There is no delay there.
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Don't forget you have enter a cable velocity factor or it will use a "canned value" (0.66%??) which may or may not be correct for the cable you are testing.

- Herb

I found a place (manage button) where I am supposed to be able to take a screenshot from VNA but that was grayed.

The screenshot functionality depends on firmware version - the software has
not been able to determine your firmware version, and it has not detected
the screenshot command ("capture") in the command list.

Upgrading your firmware is probably a good idea.

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Rune / 5Q5R

Ok. But which version, last time I checked there were so many version that I couldn't take any.

On Mon, Jan 13, 2020 at 10:37 AM, Leif M wrote:

Ok. But which version, last time I checked there were so many version that I couldn't take any.
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Leif,
One of our members compiled a table listing the different firmware available (see attachment). It should help you to narrow down your choice.

- Herb

Thank you. I managed to update the firmware and with 0.54 version too.
Is your list complete, I thought that were more. It looks so simple in the list.
About the cable length, I wish that the delay from TDR would show also in VNA_saver. It shows now as a screencapture.

On Mon, Jan 13, 2020 at 03:07 PM, Leif M wrote:

" I managed to update the firmware and with 0.54 version."
- Great. That should give you access to the latest firmware features of your choosing and offer better compatibility with the latest software versions. Plus, in the future you can enter DFU mode from the menu instead of needing to jumper the boot pins. After you successfully upgrade once then the apprehension of doing so is pretty much gone.

"Is your list complete, I thought that were more."
- The group member who created the firmware list narrowed it down to the latest versions instead of also including confusing prior versions.

"About the cable length, I wish that the delay from TDR would show also in VNA_saver. It shows now as a screencapture."
- Not quite sure of your meaning. If you mean you would like the cable length in NanoVNA-saver to be displayed as a marker value in units of time and distance, as it is on the NanoVNA TDR screen, then you need to request a feature change to Rune.


- Herb