Re: NanoVNA port renormalization
Hi John,
As Nizar mentioned renormalization is not available on my NanoVNA which is the NanoVNA-F. This morning I decided to improve my measurement dynamic range so I replaced my L pad matching networks with binocular core transformers that I wound using 2 turns on the primary and 5 turns on the secondary. This does not yield a perfect transformation for a 50 to 330 ohm impedance system but its close (it provides a 50 ohm to 312.5 ohm transformation). Using the transformer improves the dynamic range a lot because the transformers eliminate the 27.74 dB loss encountered when using the two L matching pads.
I've attached a picture of my new plot using the transformers in place of the L matching pads, and I've also attached the Murata datasheet for my ceramic filter and it looks very similar to my results.
Since I don't have a NanoVNA that has normalization I'm going to go and use LTSpice to simulate what happens to the bandpass characteristics of the ceramic filter when it's not properly terminated into its input and output impedances versus when it's terminated into its input and output impedances so see if that provides some clarity to my thinking, as my original instinct is exactly what Roger previously said which is as follows: "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." I might also use my signal generator and scope to measure the passband characteristics using various loads to see if we are dealing with a linear or non linear response.
Just FYI, and thanks for the discussion.
Don
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Re: NanoVNA port renormalization
Don,
I didn't do that for this test, but at some point in the past I did all that. I had unknown crystal filters and used the NanoVNA renormalization to find the Z that gave the best looking response, then made matching networks to test and then use them.
How does your filter look if you connect it directly (no matching) and use the renormalization?
--John
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On Thu, Feb 13, 2025 at 04:57 PM, Donald Kirk wrote:
Hi John,
I'm a little late to the party but this topic peaked my interest and my
thinking is very much aligned with Rogers. I think the one comparison test
you are missing is what filter response curve you get if you properly
terminate the input and the output of the ceramic filter during measurement on
the NanoVNA using simple resistive L matching pads as follows:
Assuming the input and output impedance of the ceramic filter is 330 ohms.
1) Build resistive L matching pads to match 50 ohms to 330 ohms (this would be
a shunt resistance of 54 ohms and a series resistance of 304 ohms when
rounding off values).
2) Connect the 50 ohm side of one matching pad to Port S11 on the VNA and
connect the 50 ohm side on the other matching pad to Port S21 on the VNA, and
connect the 300 ohm side of each matching pads together (this should be done
with your fixture in place but the Ceramic filter replaced with a wire
connecting the 300 ohm sides of the L matching pads together.
3) Do a through calibration on the VNA (this should zero S21 Logmag and S21
Phase to zero.
4) Replace the above mentioned wire that connected the two matching pads
together with the ceramic filter and observe the S21 Logmag filter response on
the VNA and this should become your baseline frequency response curve to
compare with your other methods.
My fixture was not perfect (yours looks much better) as my components had
reasonably long leads and the one thing I noted is that I needed a very good
ground plane connected to the common on my test fixture. My goal was to
measure insertion loss as well as the 3 dB and 20 dB Bandwidth for comparison
with the stated specs of the 10.7 MHz ceramic filter I was testing (part
number SFE10.7MA5-A which was sold by good old Radio Shack).
Here is what I measured.
Insertion Loss = 3.0 dB (spec 6 dB max).
3dB Bandwidth = 290 KHz (spec 280 +/- 50 KHz)
20dB Bandwidth = 540 KHz (spec 650 KHz max)
I've attached a picture showing my results
Just FYI, and I apologize in advance if you have already done the above test
that I mentioned.
Don
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Re: NanoVNA port renormalization
Hi Donald
I think what you have done physically with your Deeplec Nano-F is almost what is done by jhon but with H4 and z port renormalisation and physically cute & short connection with optimised calibration terminaisons , jhon can renormalise to any Z value quicly , Nano-F does not have this Z renormalisation option .
73s Nizar
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Re: NanoVNA port renormalization
Hi John,
I'm a little late to the party but this topic peaked my interest and my thinking is very much aligned with Rogers. I think the one comparison test you are missing is what filter response curve you get if you properly terminate the input and the output of the ceramic filter during measurement on the NanoVNA using simple resistive L matching pads as follows:
Assuming the input and output impedance of the ceramic filter is 330 ohms.
1) Build resistive L matching pads to match 50 ohms to 330 ohms (this would be a shunt resistance of 54 ohms and a series resistance of 304 ohms when rounding off values).
2) Connect the 50 ohm side of one matching pad to Port S11 on the VNA and connect the 50 ohm side on the other matching pad to Port S21 on the VNA, and connect the 300 ohm side of each matching pads together (this should be done with your fixture in place but the Ceramic filter replaced with a wire connecting the 300 ohm sides of the L matching pads together.
3) Do a through calibration on the VNA (this should zero S21 Logmag and S21 Phase to zero.
4) Replace the above mentioned wire that connected the two matching pads together with the ceramic filter and observe the S21 Logmag filter response on the VNA and this should become your baseline frequency response curve to compare with your other methods.
My fixture was not perfect (yours looks much better) as my components had reasonably long leads and the one thing I noted is that I needed a very good ground plane connected to the common on my test fixture. My goal was to measure insertion loss as well as the 3 dB and 20 dB Bandwidth for comparison with the stated specs of the 10.7 MHz ceramic filter I was testing (part number SFE10.7MA5-A which was sold by good old Radio Shack).
Here is what I measured.
Insertion Loss = 3.0 dB (spec 6 dB max).
3dB Bandwidth = 290 KHz (spec 280 +/- 50 KHz)
20dB Bandwidth = 540 KHz (spec 650 KHz max)
I've attached a picture showing my results
Just FYI, and I apologize in advance if you have already done the above test that I mentioned.
Don
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To measure insertion loss, you connect the channel 1 to the common port of the diplexor and channel 2 to one of the output ports while terminating the unused port with a 50 Ohm load. Move channel 2 to the other output port and terminate the remaining output port with 50 Ohms.
To measure isolation you connect channel 1 to one of the output ports and channel 2 to the other while termination the common port in 50 Ohms. Switch the connections on the output ports to measure the other isolation.
Gary
W9TD
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Hi Joe
You seems need an S21 Logmag measurement , Knowing that dynamic range of H4 on the UHF are limited to 50db you should not expect more then -45db values for the isolation measurements between the Two bands, obviously you need a 401 sweep points , and many complete 401 point calibrations for each bands (with isolation and Throught) , each calibration should be focused on the desired slice of the band under test, you need to reset the old calibration for each new calibration to be sure to avoid interpolation errors ,
Good Luck.
73's Nizar
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I have a NanoVNA-H4,
I have no problems checking antenna SWR etc.
But what I want to do now is to check the performance of a "Diplexor"
You know one of these things that splits/combines a 2 meter and 440 antenna into one common output.
You know one of these.
<>
I want to measure the insertion losses for each band.? and then the amount of isolation between the bands.
Can anyone show me a video on how to do this? OR give me a step by step on how to do it?
Joe WB9SBD
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a little confusion in vision between 0 and 8 on the display
Hi
May be not a very objective vision, it seems to mee that there is a little confusion in vision between 0 and 8 on the display, with SEESII H4 + DiSlord 1.2.40 , I prefer a simple 0 graphic display without the strike symbol , it will make the screen easier .
Thanks
73's Nizar .
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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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Gary W9TD
Roger Need
