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Re: Does anyone know how sensitive the nanovna is to electrostatic discharge?

 

Ouch!

Bear Burt, K6OQK

On September 23, 2019 7:03:23 AM PDT, Bear Albrecht <W5VZB.NM@...> wrote:
Caution is the keyword.
FWIW I heard long ago that nylon underwear can generate 3000 volts.

Bear Albrecht W5VZB New Mexico

--
Sent from my Android thingamabob with K-9 Mail. Please pardon the spelling errors as the dog can't spell so good.
Re: Further Comments on Resistive Bridges

 

Analog devices has a bridge and detector IC ADL5920, is this useful. It goes from 9kHz to 7GHz.
Re: Does anyone know how sensitive the nanovna is to electrostatic discharge?

 

Caution is the keyword.
FWIW I heard long ago that nylon underwear can generate 3000 volts.

Bear Albrecht W5VZB New Mexico
Re: Evaluating clamp on ferrite chokes

 
Edited

Bruce,
This link might interest you, . It describes a fixture and procedure for measuring ferrite beads using the DG8SAQ VNWA. I believe over their joint frequency range, measurements between the DG8SAQ and nanoVNA have shown close correlation.
Re: Evaluating clamp on ferrite chokes

 

On Mon, Sep 23, 2019 at 12:18 AM, Jeffrey Vandenbroucke wrote:


Coil coax around a ferrite and connect the outer shield for a S21 measurement.
Loss in S21 = choking :
Just so I understand, would I connect only the outer shield to the center pin of the two ports, leaving the center of the coax floating unconnected?
Re: Analyzing Noise versus Leakage on CH1

 

These peaks are from spurs of the SI5351 output so they move with the IF frequency and happen at 1kHz intervals.
You see them (although lower) also for the 8kHz and 12kHz harmonics of the IF
The lower the output frequency, the lower these spurs (I hope)
The temperature of the SI5351 is also expected to have an impact
Re: Noise

 

Hi Alan,
the measurements lower limit is given by the phase noise of the SAs oscillators. HP Application Note 270-2 "Autometed Noise Sideband Measurements using the HP 8568A Spectrum Analyzer" shows that typical phase noise is -110dBc/Hz between 500Hz to abt. 100kHz. So my rubidium standard is probably better than this.
You can only get reasonable results if PN of the device to be measured is worse than the analyzers own PN. There are much better ($$$$$$$) specialized PN measurement systems available now, going down to -180dBc/Hz.
Ernst
Re: Analyzing Noise versus Leakage on CH1

 

Erik,

I re-ran it at 1.2GHz, which will correspond to 240MHz. I also changed the
offset to 4KHz. Here are the results:

[image: image.png]

The 1KHz peaks are still there (and unrelated to the IF frequency). It
would be preferable that they weren't there, but we're only interested in
the peak at the IF frequency, so can we just ignore them?

Rgds,
Dave

On Mon, 23 Sep 2019 at 10:57, <erik@...> wrote:

I tested windowing and that does not make a big difference as can be
expected in this case where the stimulus is fully controlled
What is worrying me are the multiple peaks you get 1kHz apart next to the
5kHz.
Some SI5351 have difficulty locking above 250MHz (the official maximum
output frequency) and your 1.29Ghz would use a 258MHz signal from one of
the SI5351 outputs.
The 1kHz pattern is identical to what I sometimes see, but for me its
closer to 300MHz and not always.
So the 1kHz peaks are not noise but an artefact of a SI5351 having
difficulty to output the required signal.
There is already a firmware that limits the maximum fundamental to 250MHz
to avoid this problem.



image.png

Re: Analyzing Noise versus Leakage on CH1

 



For your reference here are the FFT's of the audio signal from CH1 while
connected to CH0 at various frequencies. 50 MHz, 299MHz, 1200MHz and
2100MHz, all with offset of 4kHz
Next the isolation measurements for 50MHz and 2100MHz.
This is done in my own HW so there are no changes in ADC settings, apart
from the SI5351 everything else remains the same.
With strong signals the noise floor increases max 10dB but the SNR
differences are as expected due to decrease in the 4kHz harmonic mixing
signal.
As you can see FFT'2 are rather clean. Only the 4kHz and its harmonics.
Close observation of the 4kHz shows its starts to wobble more at higher
frequencies explaining why it does not fit perfectly in the 480 samples you
use.
Hope you will be able to see the same once you have done the windowing of
the FFT input signal.

Erik,
I've separately emailed my results having added windowing to the FFT
signal. While my results are much improved from previously, the noise
spectrum is nowhere near as clean as yours. I'm assuming that although the
front-end of your setup is like the nanovna, the audio backend is different
and that you don't use the TLV3220 for ADC (your sample rate is > 200KHz?).
The nanovna has a very strong 1KHz component - probably a result of the
1KHz codec frame-rate. The CPU does a lot of processing each frame which
might be injecting noise.

Your observation of slight 4KHz wobble is a worry in that it might force
the need for a windowing function on larger samples.

Rgds,
Dave
Re: Analyzing Noise versus Leakage on CH1

 

I tested windowing and that does not make a big difference as can be expected in this case where the stimulus is fully controlled
What is worrying me are the multiple peaks you get 1kHz apart next to the 5kHz.
Some SI5351 have difficulty locking above 250MHz (the official maximum output frequency) and your 1.29Ghz would use a 258MHz signal from one of the SI5351 outputs.
The 1kHz pattern is identical to what I sometimes see, but for me its closer to 300MHz and not always.
So the 1kHz peaks are not noise but an artefact of a SI5351 having difficulty to output the required signal.
There is already a firmware that limits the maximum fundamental to 250MHz to avoid this problem.
Re: Analyzing Noise versus Leakage on CH1

 

Erik,

The FFT assumes that you have a perfect fit of the (co)sinus in the sample
range.
At higher frequencies the 5kHz start to deviate so the samples may no
longer fit perfectly in the fft and you may get spectral bleeding.
This bleeding will vary with the error of the 5kHz signal
Can you apply a window to the input of the fft and see if that clears out
the spectral bleeding?
Spot on! I applied the blackman windowing function to the 1.29GHz output
(the worst frequency), and the result is much improved - see the 10dB
improvement between 48 samples and 480 samples in the figures below. The
"spectral bleed" is replaced by a peak that is spread across just 2-3 fft
"buckets".

I ran a simple simulation and found that the spectral bleed I saw earlier
could be reproduced with a frequency of 5020 Hz, a frequency error of just
20 Hz. It appears that at some output frequencies it's not possible to
generate the LO frequency at exactly 5000Hz offset.

This very nicely explains why I got widely varying results earlier - at
those frequencies when the offset is exact, filtering over multiple frames
lifts the peak above the noise floor and improves the dynamic range, and at
other frequencies the increased filtering has no effect.

We may now have ways to move this forward and get a genuine benefit from
increased filtering. Two possible alternatives are:

Option 1. Alter the si5351 frequency setting algorithm to guarantee the Ref
and LO are exactly 5000Hz apart. This may mean having to adjust Ref
slightly from that selected, but that should not be an issue for the user.

Option 2. The dsp implements a windowing function. This option isn't as
attractive as option 1, because I believe windowing degrades the noise
margin improvement. Implementing the blackman, or many of the other
windowing functions would be too onerous for this poor little
microprocessor. However, I've simulated a simple triangle windowing
function and it shows very similar results to blackman at the peak, which
is the only area we're interested in. A triangle window would be easy to
implement.

Rgds,
Dave
[image: 1_1.29GHz_48.png]
[image: 2_1.29GHz_480.png]

1_1.29GHz_48.png
2_1.29GHz_480.png

Re: RX-Port Input Impedance

 

To get a better CH1 input impedance I recommend to use a 10dB attenuator possibly with a 10dB amplifier when above 300MHz
Re: Analyzing Noise versus Leakage on CH1

 

Indeed, that is what I plan to do with my own build VNA using (almost) the same HW as the nanoVNA
Will let you know once done
Re: NanoVNA Saver

 

Hi Rune, thank you very much for the improvements made to the NanoVNAsaver application. If not too demanding to accomplish, you would like to be able to define multiple segments, for which you can choose StartFreq StopFreq StepSize.
Your application makes nanoVNA a truly powerful tool.
Best Regards
Maurizio IZ1MDJ
Re: RX-Port Input Impedance

 

I measured the CH1 RL with a professional VNA and got this values:
100MHz 36dB
300MHz 28dB
500MHz 23dB
700MHz 20dB
900MHz 17dB

Measuring UHF filters would benefit from having a better termination impedance.

I tried to understand the CH1 input attenuator but i don't find any explanation to that topology. Using the SA612 input as single-ended, connecting IN_B to ground through a capacitor as indicated in the datasheet and simplifying the attenuator to a PI or just L arrangement could lead to a better RL with same loss. But i'm sure i'm missing something, as VNWA3 uses the same circuit although with different resistor values. It's input match is much better BTW. Maybe SA612 noise?

Carlos
Re: NanoVNA Saver

 

Hi Tom,
good suggestion! I'll have a look, and there should be plenty of room for
it! :-)

--
Rune / 5Q5R

On Mon, 23 Sep 2019 at 07:31, Tom VA7TA <tma.7ta@...> wrote:

Hi Rune,

I have made a large number of routine impedance measurements using
your V0.0.10 exe binary under Windows 10 Pro 64b. I have not encountered
any stability problems and in general think it works wonderfully well -
thank you!

One part of the GUI that I didn't understand intuitively the first
few times I used it was the purpose of the "Segments" box. I changed it and
nothing seemed to happen. I of course noticed immediately that it is a
multiplier for the number of steps in the sweep once I changed it and then
happened to do a calibration which shows the number of steps in the sweep.
I decided I would like to make a suggestion that I hope is worthy of
consideration.

It occurred to me that it would be obvious to the user that the
segments setting increases the sweep frequency resolution if the number of
Hz per step could be shown. Additionally I think the provision of the
"Hz/Step" information would be useful in some situations. For example when
sweeping a network with narrow high Q responses the user may wish to select
a segments setting that provides a sufficiently small step size to ensure a
narrow peak or null is not missed without increasing the sweep time any
more than necessary. A second advantage for providing the "Hz/Step" data is
that it would provide immediate indication of how a change of the segments
setting changes the sweep resolution. This feedback would make the setting
more user intuitive I think.

Considering that the number of segments would never exceed two
digits and the number of Hz per step would never exceed 7 digits there
might be room to fit the two boxes on the existing segments line within the
GUI. If for example the "Segments" label were abbreviated to "Segs." with a
two digit box then possibly there would be room for another label something
like "Hz/Step" followed by a 7 (or 9 if 2 comma delimiters) digit box on
the same line. Just might be one of many possible ways to implement it
without impacting the existing GUI layout very much.

Thanks again for your great contribution - "NanoVNA-Saver" really
enhances the usefulness of my nanoVNA for what I intend to use it for!

Enjoy!
Tom
VA7TA
Re: NanoVNA Saver

 

Hi Pete,
you don't need to reset the NanoVNA calibration - it probably even works
better if you don't, in that the data received from the NanoVNA will not be
rejected as mangled during data transmission if it "looks like" real data.
;-)

--
Rune / 5Q5R

On Mon, 23 Sep 2019 at 03:19, Peter Mulhare <peter@...> wrote:

Hello Rune,

Again thank you for your perseverance with the nanoVNA PC Software you are
bringing us all! It is very much appreciated.

However I have a question regarding Calibration using your software, I
presume that before I set about doing a Calibration in nanoVNA-Saver, and
reset it, I should also do a reset of the VNA Hardware itself? Or is this
taken care of by nanoVNA-Saver? As I still see the "0" come up alongside
the "C" in the left hand sidebar.

73's
Pete
ZL2iK



-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Rune Broberg
Sent: Monday, 23 September 2019 07:37
To: [email protected]
Subject: Re: [nanovna-users] NanoVNA Saver

For those waiting for new binaries: I just published 0.0.11 :-)

This release brings averaging as a new feature: Press "Sweep settings" to
select between running a single sweep (of optionally multiple segments), a
continuous (live) sweeping of the range, or to average several sweeps from
the NanoVNA. You can configure how many averages to make, and optionally,
how many of the sample points to discard, based on which deviate the most
from the rest, and are least likely to contribute signal.

Also added is a new Resistance/Reactance chart, which shows both the R and
X component of R+jX. This brings the challenge of showing two traces for
the same data - added is therefore the option of picking a secondary colour
for sweeps under "Display settings".

There are further improvements to UI sizing, meaning the interface now fits
- tightly - on a 1366x768 screen, at least on Windows.

A few quality of live improvements made it in: Press escape in any of the
pop out windows to close them instantly. The calibration window now shows
more clearly when the source of calibration data is loading from a file,
and also the number of points loaded. A few crash bugs were fixed.

I look forward to hearing feedback from all of you!



--
Rune / 5Q5R

On Sun, 22 Sep 2019 at 17:14, Mario Vano <mvano@...> wrote:

On Sun, Sep 22, 2019 at 06:09 AM, Mario Vano wrote:

CORRECTION: (I mistyped)

- The multi-band dipole is my 20ft high 40/20 meter trap dipole that has
been augmented with parallel dipoles for 15 and 10. The feedline has a
toroid common mode filter.


I've been happily using the NanoVNA and various versions of "Saver" for
a lot
of projects lately, but some were just motivated by curiosity about the
device.

Unfortunately I have no other analyzer to compare to. In any case here
are
some sweeps from earlier tests that might be useful for reference or
amusement. In most cases, they were done with my very early attempts at
full
bandwidth calibration.

- The fm filter is a commercial product from the rtl-sdr.com people.

- The LW filter is a homebrewed design I use to augment VLF beacon
hunting.

- The multiband dipole is my 20ft high 80/40 meter trap dipole that has
been
augmented with parallel dipoles for 15 and 10. The feedline has a
toroid
common mode filer.

- The 6 meter antenna is an attic mounted dipole with a toroid common
mode
filter.

I've also used happily used the device and "saver" to design and build
a
6
meter "squalo", but forgot to save the files from the latest testing
run. I'm
currently working on a 400-700 mhz indor LPA design and plan to try to
use the
device for relative pattern and gain testing.

Earlier tests with several types of 500-900mhz 1/4 wave mag-mount
antennas and
TV rabbit ears showed useful relative gain results at 2-3 wavelength
spacings.

73, AE0GL
Re: Firmware with arbitrary scan length

 

Hi Rune,
Thanks a lot for your work on NanoVNA-Saver. However it would be great to have averaging option in the standalone firmware too. It should be easy to do, i just need to find some time to get my hands on the code. Maybe next century :(

Carlos
Re: Analyzing Noise versus Leakage on CH1

 

Very interesting work, Erik. Maybe what we need is to use two separated Si5351 to avoid LO to stimulus leackage. They are cheap!
Re: Noise

 

Here is the CH1 ADC input signal analyzed with a FFT for both 50MHz and 2.099GHz, both with cable connecting CH0 and CH1 (thru) and without any connection (isolation)
The phase noise of the SI5351 is visible in the 50MHz thru graph.
Dynamic range for 50MHz is 64dB due to leakage.
The signal level for 2.1GHz is 40dB down due to being the result of a 7/9 harmonic mixing.
The "leakage" for 2.1GHz is 10dB up compared to 50MHz
Net result is a loss of 50dB dynamic range leaving 14dB at 2.1GHz

Thru 50MHz.PNG
Isolation 50MHz.PNG
Thru 2100MHz.PNG
Isolation 2100MHz.PNG

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