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I believe the main function of the shielding in this design is to improve isolation between the signal source and the SA612 receivers (so, to W5DXP’s question, I doubt there’s much improvement at HF, but this would need to be verified).

Other comments...

Mike you can make the dual shields and install them fairly easily. Make one small rectangle to cover one of the sections, and then make a similar shield, but with one of the long sides bent up, that will cover the other section.

Solder the first shield to the board per qrp rx’s Soldering recommendations, then place the second shield on the board, solder it’s 3 sides that touch the board to the board, and then solder the lifted (fourth) side to the top of the first shield.

It’s worthwhile investigating qrp rx’s suggestions. I will note:

1. Capacitive coupling to ground via the shield might be an issue, but a big question I have is how much difference in noise you are seeing. For example, if you were to short either c26 or c27 to ground, I would expect the noise floor to increase by 6 dB ( or is it 12 dB?) after recalibration. Attenuation due to capacitive coupling to ground will be less than this. So if you are seeing a large increase in noise, I would doubt that it is capacitive coupling. But do not rule it out as the cause without first verifying.

2. Similarly, I am hesitant to say that the shield itself, because only three corners are tacked to ground, is somehow injecting noise. The many ground visa should already be providing a low impedance ground path. Could there be a “slot antenna” effect due to the gap that is somehow injecting interference? Possibly, but from experience with my own designs and testing for EN61000 (and FCC) radiated and susceptibility compliance, I haven’t come across a poorly installed shield being worse than no shield. Still, do not remove it from your list of suspects until you have verified that it is NOT the problem — while I haven’t seen this as a problem, myself, QRP RX might have come across it in their designs.

3. Also, before each test, make sure you verify that the calibration is correct ( I have had some strange calibration effects). Verify that for S11 the SOL loads appear on the Smith Chart where you expect them, and verify that S21 looks correct with and without the thru jumper. (In other words, don’t rule out operator error!)

4. Finally, just a note that, although you or I might think the designs are identical, they need not be. Parts have tolerances (and might even be counterfeit). There could be manufacturing errors, etc.

- Jeff, k6jca

To better understand the performance of the nanoVNA I did a small comparison with my home build VNA.
This home build VNA uses the same SI5351, the same three SA612 mixers but instead of an embedded ADC the output of the SA612's is send to the line in of a PC and the DSP algorithms are run on the PC.
I was expecting a bit better performance for the nanoVNA as the home build VNA is dead bug style which is not optimal at high frequencies.
All measurements are done with a 1ms audio sample at every frequency point (this is the nanoVNA default without averaging) and between 500kHz and 1500MHz after calibrating with the same calibration set and the same calibration parameters (all set to zero)

First two pictures show the measurement of the "open" directly after calibration. Very comparable except for a bit more noise in high frequencies for the nanoVNA because the home build VNA uses 192kHz audio sampling and the nanoVNA uses 48kHz. Enabling 4 times averaging in the nanoVNA is expected to deliver comparable levels of noise
The sporadic peaks in the home build VNA are the artifact of some remaining problems in the audio synchronization. Too complex to explain here.....

The second two pictures compare the nano and the home build using a 30cm semi rigid open coax connected to port 1 reference plane. Reference plane extension is then set to the end of the semi rigid coax (2930ps) to have easy phase comparison. The amplitudes of both VNA's (red lines) show similar performance, a bit better for the home build. Both perform well till 750MHz but the nano phase (purple line) starts to deviate at 700MHz where the home build is acceptable till 850MHz.

The third set of pictures compare the nano and home build using a 25ohm resistor connected to the reference plane. Blue is R (starts at 25ohm), purple is JR (starts at 0 jOhm). The nanoVNA performs very well till at least 900MHz. The home build shows some deviation between 300 and 900Mhz and goes completely of track above 900MHz.

The on board ADC in the nanoVNA does support 192kHz and it should be possible to increase the signal levels for the reflection and reference SA612 to reduce noise.
The nanoVNA bridge has phase problems above 750MHz. Probably due to stray capacities in the layout. Although you can calibrate the nanoVNA till 1500MHz do not expect any relevant S11 measurements above 750MHz until it becomes possible to calibrate out the phase errors in the bridge.

Overall I'm happy with my own build and adding the ability to calibrate the phase of the bridge will also be of benefit. So I know what my next SW improvement will be

On Mon, Oct 21, 2019 at 03:22 PM, Mike_nano wrote:

However, how would you address the fact that the second one I got with no shields works better?

this is because shield installed incorrectly, it affects circuit performance.

Perhaps this PCB design doesn't come with shields because they aren't designed to need them?

Shield is needed. But this PCB has some design mistakes which makes proper shield installation more hard. Probably this is why they don't installing shield, they just don't wanna spend time to fix these issues caused by poor PCB layout.

Hi Bryan,
there's a 0.3.1 out now - as far as I can tell, it only reverses the sign
of "group delay", so not a big change. I don't think it should affect your
measurements, but I thought I would mention it.

--
Rune / 5Q5R

On Mon, 21 Oct 2019 at 09:35, Rune Broberg via Groups.Io <mihtjel=
[email protected]> wrote:

Hi Bryan,
I haven't tried the 0.3.0 firmware yet. Looking at the (sparse) release
notes, it's not obvious that there would be anything there that changes how
NanoVNA-Saver interfaces with it. I'll see if I can't find the time to load
it onto my NanoVNA and test it out :-)

--
Rune / 5Q5R

On Mon, 21 Oct 2019 at 07:03, bryburns via Groups.Io <bryburns=
[email protected]> wrote:

Rune,

I have been using several new features in nanoVNA-Saver 0.1.3 and think
that they are great additions.

I am trying to use edy555 firmware version 0.3.0 with nanoVNA-Saver
version 0.1.3. There are several new features in this firmware that are
beneficial to me when I cannot use nanoVNA-Saver, so I would like to keep
this firmware loaded in my nanoVNA. However, I am seeing a lot more data
errors with this version of firmware than I saw with 0.2.3 from edy555.

It

is so bad that I cannot get a reliable calibration in nanoVNA-Saver

without

using 5 averages and dropping 2 values in nanoVNA-Saver that are the
worst. This was not the case with the 0.2.3 version of firmware. With

the

new firmware and software I had to do repeated scans until there were no
obvious errors in the data for each termination/through condition in

order

to get a calibration that was reasonable. I could not use the

Calibration

assistant. The errors are often 0.25 to 0.5 dB in the S11 trace and

quite

obvious. Even data in the isolation state for through calibration had
large errors in amplitude, as much as 20-30 dB. I never see these errors
when I operate the nanoVNA by itself and simply use the displayed result.
It appears to be either something in the transfer (timing?) or something
related to scanning. Generally, there are about 3 or 4 bad samples per
scan, often at exactly the same frequency. As I have observed with some
previous firmware, the bad data is never in the first scan you do from
nanoVNA-Saver.

I have to wondered if the by-passing on the 5V power supply may be

related

to this issue. Without replacing the 5V supply or improving filtering I

am

not sure how to isolate this potential issue. Up to this point, I have
been reluctant to start modifying the hardware.

Have you been working with the 0.3.0 firmware from edy555? Has anyone
else reported this issue?

--
Bryan, WA5VAH

NanoVNASharp MOD v3 is released:

Whats new:

- added CAPTURE button, which allows to get screenshot from the NanoVNA
- completely rewritten from scratch communication layer, now it works more reliable
- improved error handling
- fixed calibration bug (calibration code is reworked and now works as expected, added RESET button for calibration)
- improved user interface for calibration (button highlighting, etc)
- fixed frequency setup issues
- improved support for different firmware versions
- improved S1P and S2P export
- added firmware version detect (firmware version now is displayed in the app title)

Current TODO list is to add support for unlimited measurement points.
Let me know if you found bugs or have suggestions :)

#nanovna #nanovnasharp #nanovnasharp-mod-v3 #nanovna-capture #nanovna-calibration

On Sat, Sep 7, 2019 at 12:05 PM, Rune Broberg wrote:

You're not trying to do the calibration via the NanoVNASharp application?

The "short" button in that resets the calibration.

This bug is fixed in the NanoVNASharp MOD v3:

I did

QRP RX,

There is no easy way (impossible) to make two sections under the larger shield and have any sort of continuous solder line to the board, so perhaps I'll just take it off. I'll take your other comments into account on the other shield but ...

... maybe it's not worth the trouble. I'm not "repairing" a broken PCB, I thought it would be an improvement. However, how would you address the fact that the second one I got with no shields works better? Are we really sure this PCB design actually requires shields at all? This PCB design (there is a different one) appears to never come with shields. Perhaps this PCB design doesn't come with shields because they aren't designed to need them? I need to find the response plot of the two traces (CH0 return loss with calibrated load and CH1 noise level with load) shown from another NaNo with shields and see if I'm wasting my time. Do you know where I can get those plots to compare mine to? It does look pretty with shields though.

Question: If the NanoVNA is used only for HF, are the shields necessary?

You could do what I did when I got my Nano back in June - use a very thin cellphone battery.It's perfectly safe and there are a couple of photos in the photo section of the forum:
/g/nanovna-users/photo/0/40?p=Created,,,20,1,40,0

Excellent information. Thanks for taking the time to provide this information.

Tom Stiles

Hi Nan -

I found the menu structure for firmware 0.2.3 -

but could not find one for the NanoVNA-H which was slightly different.

Thanks for heads up; I was unaware of any differences,
other than between two ("AA") and four trace versions.

Unlike commercial software and firmware, open source developers typically
do not coordinate with (and may be unaware of) other user documentation writers.

Could anyone please guide me to find this please?

By "latest", do you mean:



... or

I do not attempt to keep up with latest GitHub releases,
only those Hugen considers worthwhile posting to Google Drive..

It takes some time to download, calibrate and capture menu structure,
then a few more hours to tweak menu map CSS and HTML.

FWIW, some nanoVNA controls remain to me somewhat mysterious..

I surely did..

BR-Nan-vk2krn

Thanks to all for your responses.
The "Reset" menu option got me very confused but its clearer now. For example, Recall 1 and Reset only clears Register 1 and not "ALL" Cal data as I originally thought!
I used the latest NanoVNA-H firmware and then moved over to edy555's firmware 0.2.3. I found the menu structure for firmware 0.2.3 - but could not find one for the NanoVNA-H which was slightly different. Could anyone please guide me to find this please? I presume both firmware's are fine to use with my hardware bought from eBay - black, shields, USB-C , power on splash screen showed gen111.taobao.com. (eBay seller in Sydney, Australia)

Regards, Nan

Me too.

--
Regards,

Martin - G8JNJ

#66: Public Invitation : #66

Hello,

Allow us, please, to generally express our clear point of view
on these extraordinary stupid demands expressed by impotent
members of this group, by addressing in particular our valuable
collaborator in this very topic, Gary O'Neil, as follows:

Dear Gary,

We gradually read your huge valuable work and we think
that it certainly will be an honer for us if you will accept
this public invitation to participate with us, as the first
co-author of course, in a Series of Papers to be published
in our small-but-honest research journal FTP#J, with subjects
beginning with those research results that you and we
produced here - after a so hard work as productive doers
of course [*].

Therefore, if you -as well as any other Fellow in Knowledge,
of course- are interested enough in the open and free publication
on these matters, then do not hesitate to contact us, please,
at this email address :

yzavna@...

anytime you will feel that you are ready for such an attempt.

Meanwhile, as we already predicted with our very early
messages:

#8 - 21 September 2019 :
/g/nanovna-users/message/3004

#9 - 25 September 2019 :
/g/nanovna-users/message/3040

we are going to save our contributions in this group,
without any of these interfering nuisances of course,
which obscure and defame our research work, at:



Farewell !

[*] and not just as impotent totalitarian lazy talkers, whose their
main job in this particular case is dual :

- on the one hand, to hide from the innocent Common User the
fact that the least operation of any VNA is just as simply as our
two step process based totally on its measurements and nothing
else, as well as

- on the other hand, to mute the fact that there are errors in any
VNA results, which under more than less circumstances may
become so extremely large that its computed measurements
become totally unreliable.

That's all.

Sincerely,

gin&pez@arg

66#

Hi Jim

There is no substitute to hard work. Besides I have a Magic Wand ?

Kind regards

Kurt



-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af Starsekr via Groups.Io
Sendt: 21. oktober 2019 10:28
Til: [email protected]
Emne: Re: [nanovna-users] Measuring ferrite beads #test-jig



Kurt, Just read your comment above. I think you said it works by Magic, Which I believe. I will have to get a bit of experimenting experience before I try ferrite beads I think.



Jim, KA6TPR

Also it seems that this PCB layout is not good. Because it don't allow to place shield edge on safe distance from c26, c27. Also it looks that there is impedance problem with wire to SMA connector. The wire thickness looks like too thin for two layers pcb.

But these things cannot be fixed. This is poor PCB design.

ideald shield should be soldered with no gap. Because any gap leads to ground loop. Longer gap leads to higher noise. Did you see these through holes on the pcb ground? These holes are named "vias", they plays the same role as shield soldering. As you can see, there are a lot of vias with a short distance. This is needed to avoid ground loops between front and back ground layers of pcb.

On Mon, Oct 21, 2019 at 01:04 AM, Mike_nano wrote:

What am I missing? Did I do something wrong?

yes, you did it wrong. There are two problems with your shields:
1) You're forgot to solder left top corner of shield. The distance to the ground is long, so the shield works as loop antenna and receiving noise.

2) the distance between shield and c26, c27 is too close. Short distance leads to capacitive coupling. You're needs to cut a small piece of left top corner of your shield in order to increase distance between shield and c26, c27.

Also, you didn't shown what is under the hood of the top shield. There is also may be problem with capacitive coupling due to short distance and missing soldering at some point. Also, there are needs two sections under shield for CH0. It's not clear from your photo if CH0 shield has two sections or one section.