Date   
Re: NanoVNA V2

RFy
 

I saw his schematics and RF simulation files too when it was public repository.
https://groups.io/g/nanovna-users/message/2148

Seems NanoVNA2 dev hiding his works...

Re: Analyzing Noise versus Leakage on CH1

david mugridge
 

On Mon, 23 Sep 2019 at 16:55, <erik@...> wrote:



The nanovna has a very strong 1KHz component - probably a result of the
1KHz codec frame-rate.
I opened the nanoVNA and connected the line in of a good USB audio device
to the reference SA612. But as I did not dare to do two connections the
unbalanced signal had a lot of noise. And there were 1kHz peaks independent
from the selected output frequency, possibly coming from the PC itself as
connecting the audio input to the ground of the nanoVNA gave the same noise.
Looking with a scope showed a very clean triangular 5kHz signal, although
with some jitter that might explain some of the disturbances we see.
As disconnecting the USB resets the nanoVNA U was not able to measure with
disconnected USB as I do not know how to stop the sweep (e.g.the writing to
the SI5351) from the UI

As another way to isolate the source of the 1KHz peaks I ran a test where I
adjusted the PLL in the tlv320 so it would generate a different sampling
rate. It was a one line change to tlv320aic3204.c, line 46:
I2CWrite(AIC3204_ADDR, 0x06, 0x08); /* J=8, was 10 */.

With the correct value, the frame-rate calculation is: 8.000MHz*10.7520 =
86.016MHz, 86.016MHz/(2*7*128) = 48kHz /48 = 1KHz frame rate
With the modified value, the frame-rate calculation is: 8.000MHz*8.7520 =
70.016MHz, 70.016MHz/(2*7*128) = 39.07kHz/ 48 = 814 Hz frame rate

With the correct value, the FFT at 1.23GHz is:

[image: image.png]
With the modified value, the FFT at 1.23GHz is:

[image: image.png]

The peaks are now approx. 800Hz, which closely tallies with the modified
frame-rate.

I think this is pretty good evidence that these peaks are related to the
frame-rate, not usb or Si5351. The strongest suspect is coupling from the
CPU, which does its heavy dsp processing once each frame

Rgds,
Dave

Re: Will a nanoVNA work above 1500MHz?

Erik Kaashoek
 

I use a home build VNA for measurements above 900MHz so have no interest to buy anything else.

Re: NanoVNA V2

pluto@...
 

I suggest the ADF5355 also but it is much more expensive than the ADF4351 (especially if you need two of them)...
https://www.analog.com/media/en/technical-documentation/data-sheets/ADF5355.pdf

About the screen, an interesting idea could be to use one of the Nextion Enhanced Series (2.4”, 2.8″, 3.2”, 3.5”, 4.3”, 5.0” and 7.0”)
https://nextion.tech/enhanced-series-introduction/

Diego

Re: Firmware summary

Erik Kaashoek
 

Indeed, thanks

Re: NanoVNA V2

Erik Kaashoek
 

If you want a really big screen you can easily build on yourself using very similar HW and some ebay modules.

Two ADF4351 generators, a resistive bridge and some AIM81001 mixers dead bug style on a PCB is all you need.

https://erikkaashoek.blogspot.com/2019/02/tuning-25ghz-cavity-filter-with-home.html

But I'm happy with 10% accuracy where others on this group may need 0.01% accuracy

Re: on the comparisons

Erik Kaashoek
 

Kurt,

Allow me to share my T-check excel spreadsheet.

Copy your 2 port touchstone data into the yellow cells and the graph will show the deviations

Hope I did not make a mistake in the calculations.

Re: Firmware summary

reuterr@...
 

Hello Erik,
Thank you for adding your extension to the Hugen nanoVNA version 0.1.1.

It would be nice to fill out in the "version window" the version number,
e.g.: 0.1.1 + scan, 1500MHz

It can be done in file ui.c line 385
#define VERSION "0.1.1 + scan, 1500MHz"
void
show_version(void)
{
...

See the screenshot nanoVNA_version-screen_0.1.1_DSC08138.jpg

73, Rudi DL5FA

Re: on the comparisons

Kurt Poulsen
 

Hi David

I got permission from R&S to publish their T-Check software
http://www.hamcom.dk/VNWA/T-Check.zip and http://www.hamcom.dk/VNWA/T-Check_HD_Install.zip

But that was in 2012 and now you just in the VNWA software in a custom trace right click the Expression field and the T-Check formula is filled in. Enable a trace with linear magnitude (s parameter linear) and with 0.01 per division (1%) and reference 1 followed by a press on the F2 key and the VNWA performs a full 12Term measurement of T-Check.
Of course the VNWA shall in advance be SOLT calibrated and the T-Adaptor fitted.
If a s2p file imported with full s11/s22/s21/s12 measurement The VNWA software is totally unique (and free to use) and I have several times "banged you on the head" to overcome you HP bias and fixation and get on board your wonderful VNWA hardware/Software sitting collecting dust on the shelf.
😊 😊 😊

Kind regards

Kurt



-----Oprindelig meddelelse-----
Fra: nanovna-users@groups.io <nanovna-users@groups.io> På vegne af Dr. David Kirkby from Kirkby Microwave Ltd
Sendt: 24. september 2019 10:17
Til: nanovna-users@groups.io
Emne: Re: [nanovna-users] on the comparisons



On Mon, 23 Sep 2019 at 21:04, alan victor < <mailto:avictor73@...> avictor73@...> wrote:



Hello Reg,
I brought up this question of uncertainty in measurements several
posts ago. Although the calculation is not complicated, obtaining the
parameters to find the uncertainty boundaries is a task.
The easiest one to address is S11 and there are papers published by
NIST and the Automatic Radio Frequency Test Group (IEEE) that have
addressed the exact calculations. I'll see what I can find and can post.
I was unclear what the gentleman in this thread were requesting, but I
believe it is the same information required to calculate the
uncertainty error for any VNA measurement. For S11 this would include
the directivity errors, the reflection tracking errors and the source
match errors. These are exactly the three of the five elements posted
by the NanoVNA after a cal is complete for S11 only. Additional ones come into play for S21 cal.
Hence the measurement uncertainty in S11 is a function of these three
LINEAR values which we must obtain (somehow) from the NanoVNA
architecture; i.e. the bridge and the mixers.






Once these values are in hand, it is possible to find the difference
(error) between the measured S11 and the actual.
For S11 we would find that the difference between the measured and the
actual S11 or (S11M-S11A) is given by DELTA(S11) as follows:
DELTA(S11)=(S11M-S11A ) ~ D + TR * S11A + MS * S11A^2
D is the directivity errors, TR is the reflection tracking errors, MS
is the source match errors.
Hence, devices with small reflection coefficient, the D value is the
source of the major error. While the devices with large reflection
coefficient, source match is a most significant error.
This is a very terse answer to a subject that is well documented but
not easy to answer in a brief email.
Hope this sheds some light.
Alan




I don’t have the mathematical abilities for this, but I don’t think this is an easy problem to address, as finding out the magnitude of the different errors (eg source match, directivity errors etc) is not trivial without some items that will cost more than a NanoVNA.



However, I do know some of the techniques used, the institutions doing work in this area, as well as the name of a couple of helpful people who maybe able to give advice. I will list these in the order I think of them, rather than any more logical order.😂😂



1) I am aware that the Swiss standards laboratory METAS is doing a lot of work on VNA measurement uncertainty. They have a tool for this



<https://www.metas.ch/metas/en/home/fabe/hochfrequenz/vna-tools.html> https://www.metas.ch/metas/en/home/fabe/hochfrequenz/vna-tools.html



Their algorithms are purchased. Google



VNA uncertainty METAS



2) There is also a lot of work on this area at the National Physical Laboratory (NPL) In the UK.



Google



VNA uncertainty NPL



3) Although the first paper I found on this topic is about waveguide calibration, so is not particularly relevant here, it does contain the email address of the person leading this work at NPL, who is *Nick Ridler. *



<http://resource.npl.co.uk/docs/networks/anamet/members_only/publications/report_048.pdf> http://resource.npl.co.uk/docs/networks/anamet/members_only/publications/report_048.pdf



I spoke to Nick at one of the Keysight meetings on THz measurements. He was very helpful about what I asked him about. (As a side note, I recall being quite impressed to see a piece of rectangular waveguide Nick bought along, about 100 mm long, where the cross section of the waveguide is so small that I thought it was a spec of dust. 😀😀😀)



4) Precision airlines, which are lengths of transmission line, very close to 50 ohms, are usually used for determining the error terms. The techniques for this are well documented.



5) Airlines for 3.5 mm, which is physically compatible with SMA, are readily available on eBay , (I have some myself as part of an HP 85053B VNA verification kit). The 3.5 mm airlines tend to be quite short in length, limiting their use to high frequencies.



5.5) In my opinion, for one interested in obtaining the best performance at modest cost, it is best to test with APC7 connectors. They are very high precision connectors, better than N or SMA, yet since they are not used much nowadays, they can be found quite quite cheap.



6) 7 mm (APC7) airlines are readily available at modest prices on eBay.

They can easily be obtained at up to about 300 mm in length, but they still cost more than a NanoVNA. Prices of these tend to vary dramatically, but if one waits, one will find them for a few tens of dollars.



6.5) The best APC7 airlines don't have connectors on them, but are supported by a test port at one end a short with a hole at the other end.

The centre conductor is stored in a via. These are often sold as “tested”

on eBay, despite they have no centre conductor included, so are of no use.



Slightly inferior airlines have connectors on them and the centre conductor can not be removed or lost. I would personally buy these, as the other type are difficult to handle. I have them in one of my VNA verification kits,



<https://www.keysight.com/en/pd-1000000591%3Aepsg%3Apro-pn-85051B/verification-kit-7-mm?cc=US&lc=eng> https://www.keysight.com/en/pd-1000000591%3Aepsg%3Apro-pn-85051B/verification-kit-7-mm?cc=US&lc=eng



These can be found at reasonable price on eBay, but often are missing a floppy disk.l That makes them totally useless for their intended purpose, as does the S/N of any part being different from that on the floppy disk.

If you see such a kit, you can tell the seller that, and can potentially pick up a couple of airlines very cheaply.



7) A technique known as the T-checker,



<https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ez43/1ez43_0e.pdf> https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ez43/1ez43_0e.pdf



can be used to verify the calibration accuracy of 2-port measurements. This makes use of a mathematical property that relates the 9 S-parameters of a lossless 3-port network. One of the ports is terminated in an arbitrary impedance, the measurements made at the other two points, then a simple scalar parameter is computed. *This is a very cheap technique to use*, requiring nothing more than a coaxial T piece, but it only verifies the calibration - it tells you nothing about the sources of error.



I am unaware of any standalone programs that can take a Touchstone file around generate the T- check formula, but it would not be rocket science to write one. M



8) Kurt Poulsen, who is a member of this group, has done a lot of work on calibration kits using the software designed for use with the VNWA. Perhaps Kurt can provide links to the relevant documents he had written.



9) Unfortunately the VNWA software is closed source, but there are open source versions of tools like optimisers in high school



10) There’s going to be some discontinuity between SMA & APC7 adapters due to the change in diameter of the lines. That will be less of an issue with N to APC7, as there is little change in the diameter of connectors.



11) The components for APC7 calibration kits are quite inexpensive, but still higher than a NanoVNA. APC7 loads with return losses of almost 50 dB can be found for a few tens of dollars.



12) APC7 open standards fail into 2 types

* The simplest is just a tube that acts as a waveguide beyond cutoff. The basic problem with this design is that the fringe capacitance varies depending on how far the collet protrudes beyond the reference plane which is not well defined.

* More sophisticated opens have a piece of plastic that pushes the collet flush with the reference plane. The plastic adds capacitance, but at least one then has a well defined geometry.



That’s all I can think of just now.

--

Dr. David Kirkby,

Kirkby Microwave Ltd,

<mailto:drkirkby@...> drkirkby@...

<https://www.kirkbymicrowave.co.uk/> https://www.kirkbymicrowave.co.uk/

Telephone 01621-680100./ +44 1621 680100



Registered in England & Wales.

Company number 08914892.

Registered office:

Stokes Hall Lodge,

Burnham Rd,

Althorne,

Chelmsford,

Essex,

CM3 6DT,

United Kingdom

Re: NanoVNA V2

Wolfgang Kiefer
 

Hello, Mr. Kirkby,
would it be possible to reduce your unnecessary lines to the essentials?
It would increase the readability of your inflated messages...

Re: NanoVNA V2

Wolfgang Kiefer
 

Instead of the AD8342 I would suggest the type IAM81008 in the mixer stages.
It is specified up to 5 GHz and has an easily solderable package.

Wolfgang DH1AKF

Re: NanoVNA V2

Dr. David Kirkby from Kirkby Microwave Ltd <drkirkby@...>
 

On Tue, 24 Sep 2019 at 03:24, hwalker <herbwalker2476@...> wrote:

I gleaned the following information from one of the other nanoVNA user
groups regarding nanoVNA version 2.

Wow.

What after that - a NanoVNA VNA version 3 with 4 receivers supporting
unknown thru calibration?

In all seriousness, I feel the biggest problem with the NanoVNA is the size
of the screen.

Dave

--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

Re: on the comparisons

Dr. David Kirkby from Kirkby Microwave Ltd <drkirkby@...>
 

On Mon, 23 Sep 2019 at 21:04, alan victor <avictor73@...> wrote:

Hello Reg,

I brought up this question of uncertainty in measurements several posts
ago. Although the calculation is not complicated, obtaining the parameters
to find the uncertainty boundaries is a task.

The easiest one to address is S11 and there are papers published by NIST
and the Automatic Radio Frequency Test Group (IEEE) that have addressed the
exact calculations. I'll see what I can find and can post.

I was unclear what the gentleman in this thread were requesting, but I
believe it is the same information required to calculate the uncertainty
error for any VNA measurement. For S11 this would include the directivity
errors, the reflection tracking errors and the source match errors. These
are exactly the three of the five elements posted by the NanoVNA after a
cal is complete for S11 only. Additional ones come into play for S21 cal.
Hence the measurement uncertainty in S11 is a function of these three
LINEAR values which we must obtain (somehow) from the NanoVNA architecture;
i.e. the bridge and the mixers.



Once these values are in hand, it is possible to find the difference
(error) between the measured S11 and the actual.

For S11 we would find that the difference between the measured and the
actual S11 or (S11M-S11A) is given by DELTA(S11) as follows:

DELTA(S11)=(S11M-S11A ) ~ D + TR * S11A + MS * S11A^2

D is the directivity errors, TR is the reflection tracking errors, MS is
the source match errors.

Hence, devices with small reflection coefficient, the D value is the
source of the major error. While the devices with large reflection
coefficient, source match is a most significant error.

This is a very terse answer to a subject that is well documented but not
easy to answer in a brief email.
Hope this sheds some light.

Alan

I don’t have the mathematical abilities for this, but I don’t think this
is an easy problem to address, as finding out the magnitude of the
different errors (eg source match, directivity errors etc) is not trivial
without some items that will cost more than a NanoVNA.

However, I do know some of the techniques used, the institutions doing
work in this area, as well as the name of a couple of helpful people who
maybe able to give advice. I will list these in the order I think of them,
rather than any more logical order.😂😂

1) I am aware that the Swiss standards laboratory METAS is doing a lot of
work on VNA measurement uncertainty. They have a tool for this

https://www.metas.ch/metas/en/home/fabe/hochfrequenz/vna-tools.html

Their algorithms are purchased. Google

VNA uncertainty METAS

2) There is also a lot of work on this area at the National Physical
Laboratory (NPL) In the UK.

Google

VNA uncertainty NPL

3) Although the first paper I found on this topic is about waveguide
calibration, so is not particularly relevant here, it does contain the
email address of the person leading this work at NPL, who is *Nick Ridler. *

http://resource.npl.co.uk/docs/networks/anamet/members_only/publications/report_048.pdf

I spoke to Nick at one of the Keysight meetings on THz measurements. He was
very helpful about what I asked him about. (As a side note, I recall being
quite impressed to see a piece of rectangular waveguide Nick bought along,
about 100 mm long, where the cross section of the waveguide is so small
that I thought it was a spec of dust. 😀😀😀)

4) Precision airlines, which are lengths of transmission line, very close
to 50 ohms, are usually used for determining the error terms. The
techniques for this are well documented.

5) Airlines for 3.5 mm, which is physically compatible with SMA, are
readily available on eBay , (I have some myself as part of an HP 85053B VNA
verification kit). The 3.5 mm airlines tend to be quite short in length,
limiting their use to high frequencies.

5.5) In my opinion, for one interested in obtaining the best performance at
modest cost, it is best to test with APC7 connectors. They are very high
precision connectors, better than N or SMA, yet since they are not used
much nowadays, they can be found quite quite cheap.

6) 7 mm (APC7) airlines are readily available at modest prices on eBay.
They can easily be obtained at up to about 300 mm in length, but they still
cost more than a NanoVNA. Prices of these tend to vary dramatically, but if
one waits, one will find them for a few tens of dollars.

6.5) The best APC7 airlines don't have connectors on them, but are
supported by a test port at one end a short with a hole at the other end.
The centre conductor is stored in a via. These are often sold as “tested”
on eBay, despite they have no centre conductor included, so are of no use.

Slightly inferior airlines have connectors on them and the centre conductor
can not be removed or lost. I would personally buy these, as the other type
are difficult to handle. I have them in one of my VNA verification kits,

https://www.keysight.com/en/pd-1000000591%3Aepsg%3Apro-pn-85051B/verification-kit-7-mm?cc=US&lc=eng

These can be found at reasonable price on eBay, but often are missing a
floppy disk.l That makes them totally useless for their intended purpose,
as does the S/N of any part being different from that on the floppy disk.
If you see such a kit, you can tell the seller that, and can potentially
pick up a couple of airlines very cheaply.

7) A technique known as the T-checker,

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ez43/1ez43_0e.pdf

can be used to verify the calibration accuracy of 2-port measurements. This
makes use of a mathematical property that relates the 9 S-parameters of a
lossless 3-port network. One of the ports is terminated in an arbitrary
impedance, the measurements made at the other two points, then a simple
scalar parameter is computed. *This is a very cheap technique to use*,
requiring nothing more than a coaxial T piece, but it only verifies the
calibration - it tells you nothing about the sources of error.

I am unaware of any standalone programs that can take a Touchstone file
around generate the T- check formula, but it would not be rocket science to
write one. M

8) Kurt Poulsen, who is a member of this group, has done a lot of work on
calibration kits using the software designed for use with the VNWA. Perhaps
Kurt can provide links to the relevant documents he had written.

9) Unfortunately the VNWA software is closed source, but there are open
source versions of tools like optimisers in high school

10) There’s going to be some discontinuity between SMA & APC7 adapters due
to the change in diameter of the lines. That will be less of an issue with
N to APC7, as there is little change in the diameter of connectors.

11) The components for APC7 calibration kits are quite inexpensive, but
still higher than a NanoVNA. APC7 loads with return losses of almost 50 dB
can be found for a few tens of dollars.

12) APC7 open standards fail into 2 types
* The simplest is just a tube that acts as a waveguide beyond cutoff. The
basic problem with this design is that the fringe capacitance varies
depending on how far the collet protrudes beyond the reference plane which
is not well defined.
* More sophisticated opens have a piece of plastic that pushes the collet
flush with the reference plane. The plastic adds capacitance, but at least
one then has a well defined geometry.

That’s all I can think of just now.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

Re: NanoVNA V2

IW2FDH
 

I think that the adf4351 would be better:

Main improvements compared to the ADF4350:

* Improved 1/f in-band phase noise (5 dB)
* EVM improvement of up to 30%
* Lower PFD spurs
* Wider output range: 35 - 4400 MHz
* Small frequency/phase jumps possible without band select.

Yes, it can be used as a drop-in replacement. It is fully pin and software compatible with the ADF4350.


Andrea IW2FDH

Il 24/09/2019 04:24, hwalker ha scritto:
I gleaned the following information from one of the other nanoVNA user groups regarding nanoVNA version 2.

1. The nanoVNA will eventually reach 3GHz (and at a similar price to version 1).
2. It's going to be based on the adf4350 + si5351.
3. The 3 mixers are replaced with one higher spec mixer (ad8342) that is switched between the 3 channels.
4. A variable gain amplifier is added at baseband using one opamp and switched feedback resistors for improved dynamic range.
5. The Audio codec is removed and the stm32 built in ADC is used instead.
6. The performance should be comparable or better to V1.
7. Info about the baseband VGA design: A RFIC switch is used to switch the shunt resistor in the feedback path. The switch is basically "transparent" because the off state capacitance is in the femtofarad range (it is an RF switch) which is negligible at the IF frequency. The on state resistance is small compared to the resistors being switched in. Since the amplifier gain is mainly dictated by the feedback network, and the switch is "transparent", there is nothing other than the tempco of the physical resistors that can cause a temperature dependence. The RFIC used is the same as for the receiver RF switch, and it turns out all the maxscend switches do not have the shunt diode problem (most RF switch ICs have parasitic diodes from RF input to ground which will start to conduct at lower frequencies), so it has no theoretical lower frequency limit and can be applied at the IF frequency. This is a big improvement over using normal analog switch ICs which have capacitance in the pF range.
8. Info about linearity: The code will perform a calibration of each VGA step on boot up. Since there is no temperature dependence the calibration only needs to happen once.

A preliminary block diagram is attached. You might want to treat this as hearsay until the design appears on GitHub. The design of the original nanoVNA was released in 2016 and it took almost three years for Hugen to take the ball and run with it.

Re: Evaluating clamp on ferrite chokes

hwalker
 

On Mon, Sep 23, 2019 at 05:09 PM, Kurt Poulsen wrote:


@The ( /profile/TheBoss )

Very kind of you to offer Kurt. I was an EMC project manager up until I retired, so I know how pressing deadlines are. I have time now-a-days to follow my whims and will mock up a few test set-ups on my own and see what kind of data I get. I'll use the manufacturer's data as a reference as you did in your study. I already have access to a shielded test fixture used for calibrating rf current probes up to 1 GHz, and will it as a jumping off point. If I get any data that looks promising I post to the group.

Regards, Herb

Re: on the comparisons

Reginald Beardsley
 

I think this promises to be a very interesting thread.

I spent my career solving wave equation problems. In my case, elastic rather than electromagnetic, the impedance is pure real. But the change to complex impedances for EM is not a big deal. It's still the wave equation.

I bought Dunsmore's book and am extremely displeased with what I have read so far. I regard the TDR chapter as pure marketing FUD. Trivial first year graduate level Fourier transform homework problems are presented without solution except "buy our proprietary software". In fact, there is no explanation of what the figures show in many cases. That might be acceptable in an application note. It is not acceptable in an expensive monograph which purports to be authoritative.

A transmission line is the intro 1D seismic case before going on to the complex and difficult reality of 3D. I've written 1D codes as homework problems, written 2D anisotropic codes professionally and worked on 2D & 3D codes of a range of complexity and methods. The more I look into the VNA calibration problem the more disturbed I am with what I read. I now have a strong sense that some emperors have no clothes.

My training was in the classical mathematical physics tradition, so EE jargon and conventions are often confusing. I'm learning to make the translation, but it's still a struggle. So I'm likely to misunderstand things from time to time. All one can do is press on.

I shall have more to say later.

Have Fun!
Reg

NanoVNA V2

hwalker
 

I gleaned the following information from one of the other nanoVNA user groups regarding nanoVNA version 2.

1. The nanoVNA will eventually reach 3GHz (and at a similar price to version 1).
2. It's going to be based on the adf4350 + si5351.
3. The 3 mixers are replaced with one higher spec mixer (ad8342) that is switched between the 3 channels.
4. A variable gain amplifier is added at baseband using one opamp and switched feedback resistors for improved dynamic range.
5. The Audio codec is removed and the stm32 built in ADC is used instead.
6. The performance should be comparable or better to V1.
7. Info about the baseband VGA design: A RFIC switch is used to switch the shunt resistor in the feedback path. The switch is basically "transparent" because the off state capacitance is in the femtofarad range (it is an RF switch) which is negligible at the IF frequency. The on state resistance is small compared to the resistors being switched in. Since the amplifier gain is mainly dictated by the feedback network, and the switch is "transparent", there is nothing other than the tempco of the physical resistors that can cause a temperature dependence. The RFIC used is the same as for the receiver RF switch, and it turns out all the maxscend switches do not have the shunt diode problem (most RF switch ICs have parasitic diodes from RF input to ground which will start to conduct at lower frequencies), so it has no theoretical lower frequency limit and can be applied at the IF frequency. This is a big improvement over using normal analog switch ICs which have capacitance in the pF range.
8. Info about linearity: The code will perform a calibration of each VGA step on boot up. Since there is no temperature dependence the calibration only needs to happen once.

A preliminary block diagram is attached. You might want to treat this as hearsay until the design appears on GitHub. The design of the original nanoVNA was released in 2016 and it took almost three years for Hugen to take the ball and run with it.

Re: errors of "error" models

 

Hello,

We just uploaded the currently available version of /F/L/O/S/S/ FORTRAN code:
https://www.op4.eu/code/DW20190924.7z

Check the functionality of the program, please, by using the included text files :
[INPUT.TXT] : 101 Frequencies etc, and:

[SH.SC] : Short,
[LD.LD] : Load,
[OP.OC] : Open, and
[ME.ME] : AUT

which are the real raw measurements, collected by using an HP 8505A VNA
Automatic Network Analyzer System in CW mode under HP-IB control, from
a deliberately roughly constructed UHF Ground-Plane Antenna, which was also
deliberately roughly installed just outside and in the immediate vicinity of the
metal walls of the Anechoic Chamber in our past Antennas Laboratory, in order
to produce as much as possible anomalies in the results of Rho and Zeta,
as well as of their computed uncertainties both of complex and real value,
in terms of 101 frequency steps.

Next to come : numerous related references

Sincerely,

yin&pez@arg

PS Also, take a look, please, at the related discussion "on the comparisons":
https://groups.io/g/nanovna-users/message/2913

5

Re: Evaluating clamp on ferrite chokes

Kurt Poulsen
 

Hi Herb
I did notice you already had mentioned part 2 and 3 "plowing" thru the next messages.
Well I need to have a relatively low profile as I am in the midst of a huge project so only limited time.
I first got my NanoVNA a couple of weeks ago, and it was unpacked for a week until I got a half day to play with it.
Indeed NanoVNA can measure the same data as the VNWA. Actually there is a kind of a part 4 never published as it is only some notes and a spreadsheet and some few articles, as the core material measurement in a closed cylindric chamber facilitates measurements of the material, where I eliminate the inductance of the wire/rod passing thru the core material.
Even Fair Rite does not do that, as they use a short wire thru the core. That we got of information from Fair Rite at the time we wrote the articles, but if that still applies I do not know.
If you are interested send me a mail to @TheBoss and I will offline send you what I have. I have a zip file with the relevant material.
And no it will not be published here as I have no time for responding to question for the time being.
Kind regards
Kurt

-----Oprindelig meddelelse-----
Fra: nanovna-users@groups.io <nanovna-users@groups.io> På vegne af hwalker
Sendt: 24. september 2019 01:09
Til: nanovna-users@groups.io
Emne: Re: [nanovna-users] Evaluating clamp on ferrite chokes

Thanks for the heads up Kurt. I linked to parts 2 & 3 in a subsequent reply. I found the whole series of articles to be interesting reading and hope to construct a similar Test fixture for sorting my cache of unknown ferrites into different types. It will be interesting to see how the nanoVNA performs in such an application. Noting the results you achieved using the test fixture and DG8SAQ to evaluate Type 43 ferrite cable clamps, if you still have the fixture available how about conducting a similar evaluation using the nanoVNA and letting us know if it is up to the task. With your experience in this subject matter, I'm surprised you haven't chimed in sooner.

Herb

Re: Evaluating clamp on ferrite chokes

hwalker
 

Thanks for the heads up Kurt. I linked to parts 2 & 3 in a subsequent reply. I found the whole series of articles to be interesting reading and hope to construct a similar Test fixture for sorting my cache of unknown ferrites into different types. It will be interesting to see how the nanoVNA performs in such an application. Noting the results you achieved using the test fixture and DG8SAQ to evaluate Type 43 ferrite cable clamps, if you still have the fixture available how about conducting a similar evaluation using the nanoVNA and letting us know if it is up to the task. With your experience in this subject matter, I'm surprised you haven't chimed in sooner.

Herb