Re: NanoVNA port renormalization
Hi PY2CSH
For me per example , I prefer set Z port 1 to 75 Ohm virtually and keep Z port 2 to 50 Ohm as it's physically , so it can be very handy option for who need it .
73's Nizar
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Re: NanoVNA port renormalization
? ... I personally don't see the need to have different Z for the input and output of a DUT. ... ?
How about a matching network, say matching 50 to 20 ohms?
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Re: NanoVNA port renormalization
Roger,
You are correct. There is no added matching circuitry. It's all math. The physical connections are the same for both plots.
--John
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On Mon, Feb 10, 2025 at 09:18 AM, Roger Need wrote:
On Sun, Feb 9, 2025 at 11:56 PM, John Gord wrote:
Each is shown at 50 ohms and again at a higher Z that gives a better match
Maybe I am interpreting this incorrectly. Your comparison shows with PortZ =
50 and PortZ = 430. The Smith Chart marker shows almost the same input
impedance in both cases so it appears you did not use an L pad, resistor or
transformer to get 430 ohms on input and output of filter. Is my assumption
correct?
Roger
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Re: NanoVNA port renormalization
What NanoVna are you using ________________________________ From: [email protected] < [email protected]> on behalf of Team-SIM SIM-Mode via groups.io <sim31_team@...> Sent: Sunday, February 9, 2025 10:57 PM To: [email protected] < [email protected]> Subject: Re: [nanovna-users] NanoVNA port renormalization Hi This is my point of view : Z--> option does not change the physically pot2 impedance , it remaine always at 50 Ohm +/- 1 ohm value, just firmware by computing way can display S11 or S21 as its at 75 ohm or 300 ohm , for example seting it at the accurate physically port2 50.45 ohm will gives more accurate S11 S21 displayed results , but if DUT does not run smoothly on physically 50 Ohm load , computing compensation will loos sens , so its rather to have the two Z port option one for port1 and second for port2 . 73s Nizar.
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Re: NanoVNA port renormalization
For those interested there was a long (over 300 posts) discussion of how to measure ceramic filters in another group about 5 years ago.
David Platt started it off and I have attached his 50 to 330ohm circuit that he used to measure a Murata 10.7 MHz. filter. In this case you do not need the PortZ function.
I have also attached a graphic showing how Murata suggests using series resistors to get the correct input and output impedance for measurement. The PortZ function will be useful in this case.
Roger
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Re: NanoVNA port renormalization
On Sun, Feb 9, 2025 at 11:56 PM, John Gord wrote:
Each is shown at 50 ohms and again at a higher Z that gives a better match
Maybe I am interpreting this incorrectly. Your comparison shows with PortZ = 50 and PortZ = 430. The Smith Chart marker shows almost the same input impedance in both cases so it appears you did not use an L pad, resistor or transformer to get 430 ohms on input and output of filter. Is my assumption correct? Roger
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Re: NanoVNA port renormalization
Rather than prioritizing new feature development for the NanoVNA, I would prefer to see some integrity/troubleshooting functions build in. Things like checking for internal shorts, component values out of whack, etc. Sort of a ¡°self-test¡± series of checks, to the degree that is possible.
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Re: After firmware update my nano-vna-h is behaving bizarrely.
Yep...Just went through this myself. Mine was an MS version and dislord 1.2.40 defaults to SI.
Bryan, n0luf
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Re: NanoVNA port renormalization
Second try on screenshots:
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Re: NanoVNA port renormalization
Roger,
Here are screenshots of tests with a ceramic filter and a crystal filter at 10.7 MHz (different spans).
Each is shown at 50 ohms and again at a higher Z that gives a better match.
Also shown is the test fixture and the filters I tested. There is no matching added to the fixture, just direct connections with coax leads about 3cm long. The small headers on the test fixture are the 50 ohm and short used in calibration. Not shown in the photo is the thru jumper.
--John
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On Sun, Feb 9, 2025 at 02:40 PM, Roger Need wrote:
On Sun, Feb 9, 2025 at 02:04 PM, John Gord wrote:
A crystal (or ceramic) filter response is correctly transformed by the
renormalization; I have used this feature several times.
Interesting... What was the design impedance of the filter?
I am surprised at your results because the loading greatly affects the crystal
filter characteristics. The usual way is to use a series resistance, L pad or
transformer on input and output if the crystal filter is designed for a higher
impedance and then recalculate the response from the measured results
factoring this in. Doing this is not the same as directly connecting a 50
ohms VNA and then doing a S parameter transformation (Port Z function) like
the one in the NanoVNA. I am interested in your results so please explain
the test setup and your results.
Roger
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Re: Smith Chart acting up in calibration
As a followup on this, I see the chip specific files from Huygen, but not Dislord . . . . fwiw . . .
- Tim
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On February 9, 2025 8:41:26 PM EST, Tim Dawson <tadawson@...> wrote: At one time there were specific binaries which set that flag (but otherwise identical) Not sure if they still exist or not, since it's so easy to set.
- Tim
On February 9, 2025 8:26:04 PM EST, "Bryan Curl via groups.io" <bc3910@...> wrote:
Absolutely....thanks Tim. Somehow I missed your post.
One thing Ill have to remember now is that a reset will revert it back to SI...even if I save the config.
Fred, Yes, the sma connectors are weak sauce. They are always my first suspect. My next one may have N type...but adapters may cost more than the nanovna. hi hi.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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Re: NanoVNA port renormalization
Hi
This is my point of view : Z--> option does not change the physically pot2 impedance , it remaine always at 50 Ohm +/- 1 ohm value, just firmware by computing way can display S11 or S21 as its at 75 ohm or 300 ohm , for example seting it at the accurate physically port2 50.45 ohm will gives more accurate S11 S21 displayed results , but if DUT does not run smoothly on physically 50 Ohm load , computing compensation will loos sens , so its rather to have the two Z port option one for port1 and second for port2 .
73s Nizar.
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Re: After firmware update my nano-vna-h is behaving bizarrely.
If your nanovna-H is an MS version (rather than older SI version - see label on back for hardware revision number) - then you need to go into 'expert settings' and change the 'mode' to 'MS5351', then do 'save config'.
See if that is the problem.
Stan KC7XE
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After firmware update my nano-vna-h is behaving bizarrely.
After calibrating after upgrading to new firmware NanoVNA-H.v1.2.40.dfu from dsilord, the nano vna is showing what seems to be crazy flickering SWR values even after recalibrating and trying to find any setup that needs to be repeated.
Is this a known thing? Is it indicative that my device, labelled Nano-VNA-H and running a slightly earlier DSILord 1.2.x (1.2.30 I think) should go back to 1.2.30?
Warren VA7 WPX
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Re: Smith Chart acting up in calibration
At one time there were specific binaries which set that flag (but otherwise identical) Not sure if they still exist or not, since it's so easy to set.
- Tim
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On February 9, 2025 8:26:04 PM EST, "Bryan Curl via groups.io" <bc3910@...> wrote: Absolutely....thanks Tim. Somehow I missed your post.
One thing Ill have to remember now is that a reset will revert it back to SI...even if I save the config.
Fred, Yes, the sma connectors are weak sauce. They are always my first suspect. My next one may have N type...but adapters may cost more than the nanovna. hi hi.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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Re: Smith Chart acting up in calibration
Absolutely....thanks Tim. Somehow I missed your post.
One thing Ill have to remember now is that a reset will revert it back to SI...even if I save the config.
Fred, Yes, the sma connectors are weak sauce. They are always my first suspect. My next one may have N type...but adapters may cost more than the nanovna. hi hi.
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Re: Nanovna-h and Windows 11
On Sun, Feb 9, 2025 at 11:18 AM, Stan Dye wrote:
Please see the detailed steps I provided for getting the correct driver
installed in the .pdf file at the following link. This is in the files section
of this group. Let me know if it doesn't clearly explain the solution, and
I'll update it:
/g/nanovna-users/files/Miscellaneous/DFU-mode%20Driver%20for%20Win10Win11
Stan KC7XE
I have been using the STM32 Cube Programmer (latest is now 2.19). Thanks so much for the docs and driver so I can now switch back and forth. I'm so used to the STM32 way but it's nice to be able to use the NanoVNA-App as well.
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Re: Smith Chart acting up in calibration
Thanks for the shout out, and glad that I could help!
- Tim
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On February 9, 2025 2:41:19 PM EST, "Roger Need via groups.io" <sailtamarack@...> wrote: On Sun, Feb 9, 2025 at 10:34 AM, Bryan Curl wrote:
Roger,
Resolved: You nailed the issue. I thought for sure I was an SI type but sure
enough the HW version is 4.3_MS. The flash changed it to SI.
Bryan - The first one to suggest this was Tim Dawson so he gets the credit not me...
Roger
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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Re: NanoVNA port renormalization
On Sun, Feb 9, 2025 at 02:04 PM, John Gord wrote:
A crystal (or ceramic) filter response is correctly transformed by the
renormalization; I have used this feature several times.
Interesting... What was the design impedance of the filter? I am surprised at your results because the loading greatly affects the crystal filter characteristics. The usual way is to use a series resistance, L pad or transformer on input and output if the crystal filter is designed for a higher impedance and then recalculate the response from the measured results factoring this in. Doing this is not the same as directly connecting a 50 ohms VNA and then doing a S parameter transformation (Port Z function) like the one in the NanoVNA. I am interested in your results so please explain the test setup and your results. Roger
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Re: NanoVNA port renormalization
Roger,
Most filters are passive and linear.
A crystal (or ceramic) filter response is correctly transformed by the renormalization; I have used this feature several times.
I agree that an active circuit might not be stable if presented with 50 ohm loading when designed for another impedance.
The basic idea is that a passive two-port can be fully represented in a number of different ways like Z-parameters, Y-parameters, H-parameters and S-parameters normalized to various impedances. There are formulas to convert from one parameter type to another.
--John Gord
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On Sun, Feb 9, 2025 at 10:40 AM, Roger Need wrote:
On Sun, Feb 9, 2025 at 01:23 AM, DiSlord wrote:
Here is renormalization in coppermountaintech
Analysis > Fixture Simulator > Port Z Conversion
(z)-c.html
Unfortunately the link you provided was cutoff and did not work. Hopefully
groups.io formats this one correctly...
(z)-c.html
Copper mountain Provides for several Fixture Simulations. Here is the link to
the topic.
The current Port Z function in the NanoVNA changes the reference impedance
using only the real part with imaginary set to zero.. The measurement is
still made using 50 ohms on Port 1 (CH0) and Port 2 (CH1) and a mathematical
conversion of the matrix of S-parameters measured at 50 ohms to the matrix of
S-parameters with a reference impedance entered by the user is generated. In
my opinion there is a limitation to this method in that the DUT is being
driven and loaded by 50 ohms and that only linear passive devices will yield
correct results. Non linear devices or active circuits will not be tested
with the impedance they are designed to operate with and simulation using this
method will not yield correct results. So a 300 ohm resistive attenuator
would measure OK but a crystal filter circuit that was not designed to work in
a 50 ohm system would not.
Roger
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Roger Need
VA7WPX_Warren