Re: NanoVNA Low-Z capabilities
According to theory the S21 shunt measurement is best for measuring low impedances. My experience on the NanoVNA-H4 has not been that good with this method. The CH0 and CH1 impedance should be 50 ohms for an accurate calculation and this is not the case with the NanoVNA-H and nanoVNA-H4. Adding attenuators to the test fixture helps improve things but my results were not as good as a S11 measurement.
Attached are some measurements done with S11 and S21 shunt on a 0805 SMD 1 ohm resistor. It measured 1.003 ohms on a 4 wire Kelvin DE-5000 LCR meter at 100 kHz.
Roger
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
These are very useful cheap'ish boards for creating 35MHz to 4.4GHz ..
You can set them to a static carrier or to sweep between two frequencies, up to around 4mW max output.
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
On 10/6/21 10:09 AM, Roger Need via groups.io wrote: Mark,
Since you only want to transmit one of the harmonics from the NanoVNA you will require a bandpass filter for the 900 MHz. band. Here is a link to a good online tool that can design many types of filters with standardized component values.
Once you try it out you will see that the LC component values are small values and PCB layout will be critical.
I suggest you use an off-the-shelf component. You can buy these for a few dollars and most have specs for the PCB layout.
Here is one example...
If you don't want to design and build your own PCB and enclosure you can buy filters that come in a box with appropriate connectors. Google will find quite a few in short order. yes, that's the kind of thing I was thinking of.. 40dB isolation - so you might need 2 or 3 of them, and packaging will be important. There are inexpensive off the shelf boards with a couple SMAs and the solder pads for the filters. If you can't find them, let me know and I'll ask someone who bought them recently.
|
I might leave some feedback on github (did it also in the past). But first I need to understand what might be the issue. As Chris says, it is all a little too confusing... I am still busy untanging it (as I need to get a good workflow for future NanoVNA measurements...) Op wo 6 okt. 2021 om 18:34 schreef Roger Need via groups.io <sailtamarack= [email protected]>:
On Wed, Oct 6, 2021 at 09:01 AM, Jim Lux wrote:
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 original author of NanoVNA Saver, Rune, developed a very nice program
and graciously shared it with the user community. He was very responsive
to comments in this group and corrected bugs quickly and added many user
requested features.
Sadly he became quite ill and was no longer able to work on this project.
He graciously allowed his project to be taken over by Holger M¨¹ller
(zarath) and he has released several new versions but is not active in this
group. Bugs and new features requests can me made on the NanoVNA Saver
github page.
Roger
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
Hello Kent,
That sounds like interesting work you do.
Sorry for this off-topic response but, G8EMY. What a coincidence!
_Norman, G8EYM._
Sent from my GNU-Linux ThinkPad.
toggle quoted message
Show quoted text
On 06/10/2021 18:58, KENT BRITAIN wrote: Hi Norman
Yes, CE and the FCC would consider that sweeping signal a Transient during any compliance testing.Might even get it declared Spread Spectrum hihi.? ?(That's what Lorawan is doing)? Certainly a Quasi Peak test would take it virtually to zero.? ?Just last week I had to do some patterns on an occupied frequency and had to run +37 dBm vs my usual +13 dBm to get a good plot.? ? Kept the source antenna close the ground and only had it on for a few minutes.??Yes, had some experience with OFCOM.? ?Hold 2E0VAA and G8EMY licenses.? ?I know, an 8, but it is a full license.? Kent
On Wednesday, October 6, 2021, 11:01:09 AM CDT, Norman_G8EYM <brycek.fs@...> wrote:
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?
Mark,
as I understand it, your nanoVNA would have to run its synthesizer on one fifth of your operating frequency, and so you would have to use the fifth harmonic. That's because the third-harmonic range of the nanoVNA ends at 900MHz.
To pass the rather weak fifth harmonic while rejecting the much stronger fundamental and the other harmonics, a first order filter will definitely not be good enough.
In that frequency range my best bet for a homemade filter would be a 3-resonator helical filter, made with simple copper wire spirals, on a groundplane, with shields made from copper sheet (or brass, if you can't find copper), tuned by means of brass screws through the top, and coupled through slots cut into the shield walls. There are online calculators that can design such a filter for you. Helical filters can be built without requiring any RF rated component at all, just wire, metal sheet and screws! And they give really good performance.
Using ready-made monolithic filters is probably not a good choice, because they tend to have many spurious responses. They are intended for passing a certain band and rejecting the neighboring bands, but may not have good attenuation on far-away frequencies, such as the fundamental of your square-wave signal. If you use such ready-made filters, be sure to check the specs first and make sure that they actually have good attenuation on all the far-away frequencies you need to attenuate.
A highly selective helical filter, followed by several broadly tuned amplifier stages, should do what you need.
Maybe a better solution is to not use the nanoVNA for this, but use any sort of signal generator that runs directly on the frequency you want.
Manfred
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
Hi Norman
Yes, CE and the FCC would consider that sweeping signal a Transient during any compliance testing.Might even get it declared Spread Spectrum hihi.? ?(That's what Lorawan is doing)? Certainly a Quasi Peak test would take it virtually to zero.? ?Just last week I had to do some patterns on an occupied frequency and had to run +37 dBm vs my usual +13 dBm to get a good plot.? ? Kept the source antenna close the ground and only had it on for a few minutes.??Yes, had some experience with OFCOM.? ?Hold 2E0VAA and G8EMY licenses.? ?I know, an 8, but it is a full license.? Kent
toggle quoted message
Show quoted text
On Wednesday, October 6, 2021, 11:01:09 AM CDT, Norman_G8EYM <brycek.fs@...> wrote: 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?
Mark,
Since you only want to transmit one of the harmonics from the NanoVNA you will require a bandpass filter for the 900 MHz. band. Here is a link to a good online tool that can design many types of filters with standardized component values.
Once you try it out you will see that the LC component values are small values and PCB layout will be critical.
I suggest you use an off-the-shelf component. You can buy these for a few dollars and most have specs for the PCB layout.
Here is one example...
If you don't want to design and build your own PCB and enclosure you can buy filters that come in a box with appropriate connectors. Google will find quite a few in short order.
Roger
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
For filter design and performance, you might try Elsie: <> It's good for lumped element filters. My first knee jerk reaction to your requirements is that you may need to go to a cavity filter to obtain the harmonic and spurious suppression you require to be "legal". Hi-Q helical filters might also get you there. I can't speak for the FCC, but once worked at the very beginning of the RFID craze (right off "The Hill" from Los Alamos) before we went public. RFID was originally developed to track radioactive transport trucks. We had an experimental license from the FCC for the 900 and 2.4 GHz ISM bands. You are likely treading on thin ice with any amount of power, however, even 3 decades ago, FCC (unofficially) considered the 902 to 928 MHz ISM band the new "junk band" (their words). Even in my relatively RF isolated location, I have quite a number of 900 MHz ISM band emissions detectable on the spectrum analyzer with nothing more than a short clip lead as an antenna. Take your chances with unlicensed emissions of any significant amount of power / antenna gain. Dave - W?LEV On Wed, Oct 6, 2021 at 11:43 AM msat via groups.io <msatoria= [email protected]> 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
-- *Dave - W?LEV* *Just Let Darwin Work*
|
On Wed, Oct 6, 2021 at 09:01 AM, Jim Lux wrote: 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 original author of NanoVNA Saver, Rune, developed a very nice program and graciously shared it with the user community. He was very responsive to comments in this group and corrected bugs quickly and added many user requested features. Sadly he became quite ill and was no longer able to work on this project. He graciously allowed his project to be taken over by Holger M¨¹ller (zarath) and he has released several new versions but is not active in this group. Bugs and new features requests can me made on the NanoVNA Saver github page. Roger
|
Re: To the RF gurus out there: bandpass filtering S11 harmonic?
FCC Restricted Bands (Part 15.205) is likely to be relevant, where the
requirement is equivalent to -41.2dBm/MHz eirp (assuming a 0dBi antenna),
-41.2dBm/100kHz 960MHz-1GHz, and -49dBm/100kHz at lower frequencies,
although it changes again as you go lower. It rather depends on where the
spurii lie. Notice these are spectral density limits.
Andy, G4KNO.
toggle quoted message
Show quoted text
On Wed, Oct 6, 2021 at 4:53 PM Jim Lux <jim@...> wrote: 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.
|
Alternative suggestion give them ear plugs. Ha ha
De K8HTB Joe
|
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.
toggle quoted message
Show quoted text
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.
|
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
toggle quoted message
Show quoted text
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
|
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.
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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
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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.
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Roger Need
Chris K2STP