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Re: Calibration result

 

On 10/6/21 8:20 AM, Victor Reijs wrote:
What I don't understand: If 'weird' measurements can be handled/calibrated
with code in the NanoVNA (which is a smallish device), why would it not be
possible to have proper calibration, without crashes (even of 'weird'
measurements) on a PC (aka NanoVNA Saver)?
It could be an artifact of how scikit-rf works or how NanoVNA-Saver is coded.

For example, the uncalibrated nanovna returns gamma for ch0 as reflected measurement/source measurement

It's easy to imagine raw reflected > raw source, so |gamma| is greater than 1.

It might be that the code doesn't allow for that.

Saver, in general, doesn't have a lot of error recovery built in - it's a nice program, but there's plenty of places where if something is wrong, it just dies, and leaves it up to you to go look at the source code to figure out how to fix it.

The plotting routines are probably more brittle than the scikit-rf routines - that's sort of typical for Python - PyQT5 works fairly well, but there are times when some assumption isn't met internally (e.g. in the data you pass it) and it gets confused.






Op di 5 okt. 2021 om 23:14 schreef Roger Need via groups.io <sailtamarack=
[email protected]>:

As I mentioned earlier the calibration routines in NanoVNA Saver depend on
having calibrated input over a wide range from the NanoVNA according to
Rune. This may be because the algorithm used in Saver does not do much
bounds checking and would not work well with raw data. I have had
instances where Saver just aborts at the conclusion of a cal routine and I
have to start all over gain.
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

Hello Kent,

Mark introduced himself as an 'RF newbie' and I was, somewhat clumsily, trying to point out that transmitting RF is not an unregulated activity. I understand that very low power CW transmissions might not be noticed. But adding an RF Amplifier could change the game.

Cheers,

_Norman._

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 16:37, KENT BRITAIN wrote:
Hi Norman
On this side of the pond the FCC does recognize the need to radiate signals during testing.
I have an antenna range and commonly transmit on many commercial frequencies.
I am expected to minimize radiated signals per "Good Engineering Practice" and are responsible for any interference I cause.? ? ? The NanoVNA certainly falls into this category.? ? Just leave it on long enough to get a good reading and you meet FCC guidelines.? ?In the real world you would probably leave it on for a week and no one would notice.? ? ?Kent
On Wednesday, October 6, 2021, 09:45:24 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:
Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a
carefully regulated and licensed activity, whether for experimentation
or any other purpose. Holders of transmitting licences are required to
adhere to the local regulations concerning frequency, power, mode of
transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions,
the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be
legal as, for starters, the 'bare foot' Nano-VNA doesn't have the
capability to be modulated and provide your station ID.

I could be wrong, of course.

Regards,

_Norman, G8EYM_

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 11:36, msat via groups.io wrote:
Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

On 10/6/21 7:03 AM, Norman_G8EYM wrote:
Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a carefully regulated and licensed activity, whether for experimentation or any other purpose. Holders of transmitting licences are required to adhere to the local regulations concerning frequency, power, mode of transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions, the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be legal as, for starters, the 'bare foot' Nano-VNA doesn't have the capability to be modulated and provide your station ID.
Amateur radio transmissions require id, as do broadcasts (both are for the purposes of "communication") but other transmissions generally do not (radars don't ID).? As it happens radars aren't legal for amateur radio in the US - the transmission has to be intended for reception by another station, except for beacons.

That's really not an issue here - the OP is talking ISM - Industrial, Scientific, Medical - in the US it's a different set of rules, some in Part 15, some in Part 18.

ISM usage (industrial microwave ovens are at 915 MHz for instance) doesn't require transmitting id. It does require compliance to the emission standards (a "field strength at X meters"? kind of measurement, typically)

18.305 has a table that says 25 microvolts/meter at 300 meter distance if your RF power is <500W for "inband" and

<10 microvolts/meter at 300 meter distance for "out of band" - that's 2.6E-13 W/square meter. (-126dBW/m2) - spread out over 4pi(300^2) (60 dBsm) - so

Max isotropic radiated power is then -66 dBW? or 0.25 microwatt. That is what's going to set your filtering requirement.? if you didn't have an amplifier, and your NanoVNA puts out 1 mW, a 40 dB rejection would probably work, unless you have a gain antenna, in which case it has to be more.

If the amplifier is putting out 10 Watts (for example), and there is a 10dBi antenna, then the OP needs 90 dB of rejection - that's quite a lot - a narrow band trap might work, reducing the number of sections required, as opposed to a 915 MHz BPF.? On the other hand, there are probably people selling monolithic 915 MHz filters? - cordless telephones use that band, for instance.

Check Johanson, Minicircuits, or Murata - it might take a couple stages, combination of high pass and low pass, and some careful layout.? Eval boards are your friend here, if it's a one off prototype.
Re: Calibration result

 

DisLord,
First, THANKS for all your efforts!! You guys do an amazing job, I want to make sure my comments are not taken as I think people are not working hard¡­.. ;-).

I¡¯m only trying to offer my very inexperienced view which I¡¯m 100% sure there are a LOT of folks in a similar situation trying to utilize the NanoVNA. All this ¡°confusion¡±/questions on exactly how to handle the calibrations between experienced/knowledgeable users only re-inforces my thoughts that more error checking and/or simpler procedures should be developed to make it more fool proof.

Case in point, I¡¯m currently not sure my results of simple antenna scans are accurate based on the above discussions. I¡¯m just missing too much knowlede, and the device/software does not account for that.

--
Regards,
Chris K2STP
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

Hi Norman
On this side of the pond the FCC does recognize the need to radiate signals during testing.
I have an antenna range and commonly transmit on many commercial frequencies.?
I am expected to minimize radiated signals per "Good Engineering Practice" and are responsible for any interference I cause.? ? ? The NanoVNA certainly falls into this category.? ? Just leave it on long enough to get a good reading and you meet FCC guidelines.? ?In the real world you would probably leave it on for a week and no one would notice.? ? ?Kent

On Wednesday, October 6, 2021, 09:45:24 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:

Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a
carefully regulated and licensed activity, whether for experimentation
or any other purpose. Holders of transmitting licences are required to
adhere to the local regulations concerning frequency, power, mode of
transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions,
the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be
legal as, for starters, the 'bare foot' Nano-VNA doesn't have the
capability to be modulated and provide your station ID.

I could be wrong, of course.

Regards,

_Norman, G8EYM_

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 11:36, msat via groups.io wrote:
Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark
Re: Calibration result

 

What I don't understand: If 'weird' measurements can be handled/calibrated
with code in the NanoVNA (which is a smallish device), why would it not be
possible to have proper calibration, without crashes (even of 'weird'
measurements) on a PC (aka NanoVNA Saver)?


Op di 5 okt. 2021 om 23:14 schreef Roger Need via groups.io <sailtamarack=
[email protected]>:


As I mentioned earlier the calibration routines in NanoVNA Saver depend on
having calibrated input over a wide range from the NanoVNA according to
Rune. This may be because the algorithm used in Saver does not do much
bounds checking and would not work well with raw data. I have had
instances where Saver just aborts at the conclusion of a cal routine and I
have to start all over gain.
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

Good afternoon Mark,

In most parts of the world, transmitting a radio frequency signal is a carefully regulated and licensed activity, whether for experimentation or any other purpose. Holders of transmitting licences are required to adhere to the local regulations concerning frequency, power, mode of transmission and harmonic content, to name but a few.

Assuming that you can conform to the required standards and conditions, the appropriate filtering methods are well documented.

My initial assessment of your planned experiment is that it wouldn't be legal as, for starters, the 'bare foot' Nano-VNA doesn't have the capability to be modulated and provide your station ID.

I could be wrong, of course.

Regards,

_Norman, G8EYM_

Sent from my GNU-Linux ThinkPad.

On 06/10/2021 11:36, msat via groups.io wrote:
Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

On 10/6/21 7:11 AM, Jim Lux wrote:
On 10/6/21 3:36 AM, msat via groups.io wrote:
Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?
Are you going to be truly fixed frequency, or are you going to sweep within ISM 908-928 range?

I'm not sure the NanoVNA-H will actually go that high - The notional range is up to 900, and it kind of depends on whether the Si PLL can get high enough. Note that there are two PLLs and they run at different submultiples (the receiver LO uses a different harmonic than the source LO)

Yes, you'll need some sort of filter. How good does it have to be? That depends on your spurious emissions requirements.. You need to look at the rules for your kind of operation - is it a "must be 60dB below desired signal" or is it a "must be below X Volts/meter at Y distance" spec.

Some sort of LC would probably work - whether you can get the ultimate rejection you need with a single LC is hard to know, but get yourself a copy of a program like Elsie (Tonne Software, free version) and you can fairly rapidly design a filter.? You'll probably also need a filter on the output of your amplifier, depending on how linear it is.

902-928, misremembered, but otherwise, same.
Re: To the RF gurus out there: bandpass filtering S11 harmonic?

 

On 10/6/21 3:36 AM, msat via groups.io wrote:
Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?
Are you going to be truly fixed frequency, or are you going to sweep within ISM 908-928 range?

I'm not sure the NanoVNA-H will actually go that high - The notional range is up to 900, and it kind of depends on whether the Si PLL can get high enough. Note that there are two PLLs and they run at different submultiples (the receiver LO uses a different harmonic than the source LO)

Yes, you'll need some sort of filter. How good does it have to be? That depends on your spurious emissions requirements.. You need to look at the rules for your kind of operation - is it a "must be 60dB below desired signal" or is it a "must be below X Volts/meter at Y distance" spec.

Some sort of LC would probably work - whether you can get the ultimate rejection you need with a single LC is hard to know, but get yourself a copy of a program like Elsie (Tonne Software, free version) and you can fairly rapidly design a filter.? You'll probably also need a filter on the output of your amplifier, depending on how linear it is.
To the RF gurus out there: bandpass filtering S11 harmonic?

 

Hello everyone!

RF newbie and first time poster here. Recently purchased a NanoVNA-H for a specific experiment I'd like to perform. Without going into the unnecessary details of the experiment itself, what I'd like to do is use the nano as a fixed RF frequency gen, probably in the ~900MHz ISM band, to be fed to an amp and transmitted via an antenna. A probe on S21 will then be used for obtaining relative phase angle measurements.

I know the nano generates a square wave output, thus the dominating frequencies are the fundamental and odd order harmonics, along with some even order and spurious frequencies. I also know that the nano will rely on the 5th harmonic of some fundamental in order to reach my desired fixed frequency. Since not only would it be irresponsible to transmit those various other frequencies, but I also think my experiment would be better served by having as spectrally pure signal as is reasonably possible. To avoid any confusion, my intended TX signal chain is as follows:
nanoVNA S11 -> bandpass filter (probably LC?) -> RF amp -> antenna

So my question is this: how sophisticated does the filter realistically need to be? Would a 1st order LC bandpass do, or do I need something else? Are there any common "gotchas" that trip up newbs that I should be aware of?

Thanks!
Mark
Re: Case for the Nano VNA

 

On Mon, Oct 4, 2021 at 10:01 AM, OiBoy The Pissed off Punk wrote:


Mine came from thingiverse. I love it.
Your radios/equipment might look good if cleaned ;)
Re: NanoVNA-F audio

 

Since the transducer/speaker is small with an even smaller opening, you can open the case and place a piece of masking tape over the opening. That will greatly reduce the level.?


On Tue., 5 Oct. 2021 at 3:55 p.m., James Laughter via groups.io<vk8tx@...> wrote: G'day all, I have the F version 1.0.3 up and running.? Is there any way to disable the audio when the VNA is turned on and each time a calibration? button selection (e.g., Open, Short, Load)?? I hope so since the family doesn't like hearing my testing.
Thanks, Jim
Re: Calibration result

 

On 10/5/21 2:13 PM, Roger Need via groups.io wrote:
On Tue, Oct 5, 2021 at 11:19 AM, Jim Lux wrote:


So that really does push one to say "NanoVNA-Saver" should send a "cal
off" command before sweeping, if you're doing cal within NanoVNA-Saver.
As I mentioned earlier the calibration routines in NanoVNA Saver depend on having calibrated input over a wide range from the NanoVNA according to Rune. This may be because the algorithm used in Saver does not do much bounds checking and would not work well with raw data. I have had instances where Saver just aborts at the conclusion of a cal routine and I have to start all over gain. I have never had this problem with the NanoVNA app by OneOflEleven.

Interesting.. maybe it doesn't handle reflection coefficients with mag > 1 or something. That could easily happen if it's uncalibrated, since it's just returning reflection/source, and the gains of the two paths are different.


Since I'm trying to modify -saver to handle two nanovnas, I'll dig into it.
Re: Calibration result

 

On Tue, Oct 5, 2021 at 11:19 AM, Jim Lux wrote:



So that really does push one to say "NanoVNA-Saver" should send a "cal
off" command before sweeping, if you're doing cal within NanoVNA-Saver.
As I mentioned earlier the calibration routines in NanoVNA Saver depend on having calibrated input over a wide range from the NanoVNA according to Rune. This may be because the algorithm used in Saver does not do much bounds checking and would not work well with raw data. I have had instances where Saver just aborts at the conclusion of a cal routine and I have to start all over gain. I have never had this problem with the NanoVNA app by OneOflEleven.

Roger
NanoVNA-F audio

 

G'day all, I have the F version 1.0.3 up and running. Is there any way to disable the audio when the VNA is turned on and each time a calibration button selection (e.g., Open, Short, Load)? I hope so since the family doesn't like hearing my testing.
Thanks, Jim
Re: Calibration result

 

On 10/5/21 11:13 AM, DiSlord wrote:
Difficult implement fast vector interpolation on this CPU:

NanoVNA measure real imag, for convert it to Z angle need:
Z = sqrtf(real*real + imag * imag)
angle = atan(real, imag); // here more difficults, need get correct sign

After interpolation need back to real imag, also need prevent change angle from 360 degree to 0, lot of mathematic for this small device (H and V2 not have hardware FPU, so any float calculations emulated, slow) ?


Linear interpolation work good, but need know this limits

So that really does push one to say "NanoVNA-Saver" should send a "cal off" command before sweeping, if you're doing cal within NanoVNA-Saver.
Re: Case for the Nano VNA

 

I create this case for my 4 inch nanoVNA v2:


it contain stick holder, and box for calibration kit, not big.
Re: Calibration result

 

Thanks DiSlord for explanation, I understand.

Op di 5 okt. 2021 om 20:13 schreef DiSlord <dislordlive@...>:

Difficult implement fast vector interpolation on this CPU:

NanoVNA measure real imag, for convert it to Z angle need:
Z = sqrtf(real*real + imag * imag)
angle = atan(real, imag); // here more difficults, need get correct sign

After interpolation need back to real imag, also need prevent change angle
from 360 degree to 0, lot of mathematic for this small device (H and V2 not
have hardware FPU, so any float calculations emulated, slow) ?


Linear interpolation work good, but need know this limits
Re: Calibration result

 

Difficult implement fast vector interpolation on this CPU:

NanoVNA measure real imag, for convert it to Z angle need:
Z = sqrtf(real*real + imag * imag)
angle = atan(real, imag); // here more difficults, need get correct sign

After interpolation need back to real imag, also need prevent change angle from 360 degree to 0, lot of mathematic for this small device (H and V2 not have hardware FPU, so any float calculations emulated, slow) ?


Linear interpolation work good, but need know this limits
Re: Calibration result

 

Hello DiSlord,

Should the interpolation not be based on radial interpolation: so average
of modulus and average of angle? All things here are complex numbers, so I
think that we should also do a complex interpolation.
Or do I misunderstand?

All the best,

Victor

Op di 5 okt. 2021 om 19:18 schreef DiSlord <dislordlive@...>:

Better do one calibration or on NanoVNA or on CPU side
Calibration data contain noise, this noise added to calibrated value
(increase noise), after send to CPU and use as basic calibration in CPU
side, and additional increase noise after.

About interpolation, NanoVNA use linear interpolation, and if
phase/amplitude rotate fast between points - can give big error (see image):
Exist 2 points, on linear interpolation used line, so result vector - red
point, but correct value - green point. On small phase between 2 points
error small, but on big ... can be wrong
Bigger point count - reduce phase/amplitude shift

V2 - have this problem in range < 30MHz, so need calibrated in 2 ranges
1MHz to 140MHz and 40MHz - max (on less 1 MHz better add additional
calibration)
H/H4 - not critical calibrate in 1 to 1500MHz range (but also have
problems in harmonic change near 300, 900MHz at this point i use
extrapolation, this reduce error, but not remove it)
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