Re: VNA Help for microwave analyzers
Very interesting site, much to study in depth to learn more about VNA and CALKIT.
I suggest inserting the link on the wiki page
Maurizio
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Re: Firmware with arbitrary scan length
Carlos,
Rune's next release of nanoVNA Saver will introduce "Averaging, including truncated mean. First version. " I am interested in seeing how users who have been requesting averaging for the nanoVNA will respond.
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Re: Firmware with arbitrary scan length
On professional VNAs, stimulus source is calibrated for flatness on factory with a bolometer. On nanoVNA you can't control stimulus output power, so we should probably calibrate the audio codec gain to get most of it's dynamic range at each frequency, or at least for each band. However multiple mixing products, others than the desired one, could be present at audio frequencies, so this must be done with care.
This could also lead to a debate about needed headroom to measure DUTs with gain. IMHO, it would be better to sacrifice having a lot of headroom and just insert an attenuator if an amplifier S21 is to be measured.
I have not taken a look to the code in much detail yet, maybe this is being done, but probably not. I have read somewhere that people have measured their LNA's gain, so current code must be setting the codec gain too low if it has so much headroom and the S21 70-80dB noise floor we are seeing could be in fact being limited by the codec dynamic range.
I also miss an averaging mode, as some measurements are quite noisy, and it would help for duplexer adjustments with notches near the VNA noise floor. Maybe just a moving average low pass filter with just 2 taps to avoid increasing memory requirements (new=0.9*last+0.1*meas). David mentions using averaged measurements for isolation, and in fact most professional VNAs use averaging when performing calibration.
Carlos
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Re: NanoVna Menu Scroll Switch Repair Replacement?
It's been my experience what I've had problems with a vendor that they beg you to
give them a positive report if they fix the problem. And generally they will jump
through hoops to do it. Have a conversation with the vendor and take your choice,
a replacement or a refund. But DON'T give feedback until the issue is resolved.
Bruce, K4TQL
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Re: Analyzing Noise versus Leakage on CH1
David,
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.
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VNA Help for microwave analyzers
I use this SW for many tasks and interface via the HPIB bus to load calibration tables for my VNA(s).
There are tips and application notes and excellent information at this site.
The SW is free down load.
An arrangement of this type SW with the NanoVNA added would be a significant assist. Up loading via USB.
My search on this site shows no prior mention of this tool, so find it added below:
Alan
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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
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Re: Further Comments on Resistive Bridges
Ideal resistive bridge response:
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Re: Advice sought on specific measurement.
Hans,
The tdr function, available standalone in the recent firmware upgrades and connected to a pc via software program, is good for evaluating cables. It can give you info about discontinuities, cable length and impedance bumps. I measured a 25 ft length of RG58 cable using the tdr option of Rune's nanoVNA Saver program and it found a short at 5 ft from the end of one of the connectors. Saved me the grief of installing a defective cable in my ham shack.
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Re: Does anyone know how sensitive the nanovna is to electrostatic discharge?
On Sun, Sep 22, 2019 at 03:15 AM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:
On Sun, 22 Sep 2019 at 08:10, Dr. David Kirkby <
drkirkby@...> wrote:
I fail to see the need to worry if the active devices is connected across
a 50 ohm resistor. 50 ohms is effectively a short circuit as far as static
is concerned.
Here¡¯s a video from dave Jones of EEVBLOG measuring the DC resistance of
antistatic mats.
Two DVM probes are put next to each other, the meter, which can read upto
300 M ohm can measure anything.
I should have said that the meter can not measure the resistance - it is
over 300 M ohm.
You are not going to zap the NanoVNA with static on its RF input terminals.
--
Dr. David Kirkby,
David, antistatic mats are typically constructed of 3 layers: the outside being a work surface of some plastics composition and the middle is the conductive portion. What was done in the video was not a valid test. He should have used a surface charge meter to measure. The whole idea is to bleed off any charges, not to 'short' them at the work surface. The middle layer of the work mats is made up of a carbon weave and yes, it conducts. Folks also need to know that these mats need to be grounded or they're useless. Many times in dry weather, I've gotten up from my chair and placed my hand at the edge of the mat to be greeted with a nice zap every so often. Shocking! Larry
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Re: Using nanoVNA to measure the directivity of a directional coupler
tuckvk3cca,
Thanks for the feedback. I finally was able to find a directivity specification of 20 dB minimum for the Narda 3060-20 on the web, which is in agreement with my measurement made using the nanoVNA. My best directional couplers have a 40 dB directivity. The ones I own with a directivity below 20 dB I only use for indicative purpose.
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Re: Advice sought on specific measurement.
For evaluating cables I normally just do a S21 log measurement, which is somewhat of a "catch all" test for losses due to impedance problems, cable defects etc. I only calibrate with a "through" measurement (with a union connector in place where the CUT will eventually be placed). Then I make the S21 log measurement with the cable being tested in place (where the union connector was during the through calibration). The frequency range depends on the needs...but higher frequencies near the nanoVNA upper limit will certainly be more sensitive in terms of detecting differences in cable performance.
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Re: Will a nanoVNA work above 1500MHz?
Further investigation did show the dsp algorithm fails to detect the intended signal but locks on a different harmonic so only thru measurement with a filter that removes unwanted fundamentals and other marhonics may ever be possible.
On similar hardware (SI5351, resistive bridge and 3*SA612, but much more selective dsp filter) I was able to have 20dB dynamix range at 2GHz but also there the bridge lost most/all directivity.
I guess for now impedance measurement at 2GHz will not be feasible with a nanoVNA
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Re: Using nanoVNA to measure the directivity of a directional coupler
30dB is rather low for 10MHz. I can get 53dB at 10MHz and 37dB at 35 MHz but this was not measured with the nanoVNA.
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Re: Using nanoVNA to measure the directivity of a directional coupler
At step 3 you can also use a shorted load. Then you have directivity for short. The two should be close about 0.5 dB. Also reverse IN and OUT to check symmetry.
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Re: Will a nanoVNA work above 1500MHz?
Thank you for the link.
I could not run the program. Many of the menue options do not respond.
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Advice sought on specific measurement.
I want to use my NanoVNA to determine if the cables I use in my lab are good enough, like the correct Z, no sharp bends or crushed dielectric or bad connectors, and so on.
My first vague idea was to
1. Calibrate solt for a plane at the end of a short cable.
2. Connect the cable under test, the CUT, to the end of the short cable in 1.
3. Connect something, (short, open, load?) at the end of the CUT.
And then know what a perfect CUT with Zc= the load test R would look like on the NanoVNA display.
And that I don't know.
Can you advice on this?
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Hi Rune , I get the last version , and I will test the average function as son as possible.
Many thanks for the very good application . Next week I wil measure a notch FM filter
using the nanoVNA using nanosaver , and also an hp8752B . I will compare the measures
and post the graphics.
Best regards
Maurizio IZ1MDJ
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Hi Rune Absolutely an enjoyment to use. Keep up the good work Have not yet tried the calibration, will do. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] < [email protected]> P? vegne af Rune Broberg Sendt: 22. september 2019 09:26 Til: [email protected]Emne: Re: [nanovna-users] NanoVNA Saver Hi Kurt, thank you for trying out the app! I'll certainly consider a way to lock the markers out of mouse control. I'm looking into zooming/scaling of the plots, but I don't have a great solution figured out yet. I hope you enjoy using the software :-) -- Rune / 5Q5R
On Sat, 21 Sep 2019 at 11:58, Kurt Poulsen <kurt@...> wrote: Hi Rune
V0.0.10 works fine, thank you.
May I suggest that the selection dots for the markers had a toggle
function such that when these was not marked the were locked and when
marked the marker was moveable. Alternative a further line called lock
markers. My eager right hand fingers hit very often the left mouse key
and the active marker is suddenly somewhere else.
Also if the vertical unit were scaleable would be nice e.g. to have
selectable dB ranges in steps or freely selectable. Same applies for
polar plot to e.g. to be able to study a load close in if inductive or
capacitive or both.
Kind regards
Kurt
-----Oprindelig meddelelse-----
Fra: [email protected] <[email protected]> P? vegne af
Rune Broberg
Sendt: 18. september 2019 22:36
Til: [email protected]
Emne: Re: [nanovna-users] NanoVNA Saver
I just released 0.0.10:
It's not the most exciting release, but it offers some quality of life
improvements, such as the ability to choose the font size
(particularly useful for Linux users, whose default is a massive 11 pt font).
It also adds debug logging: -d to get log messages to the terminal, or
-D filename.txt to log to a file. Useful if you see crashes!
Additionally, it now supports importing magnitude/angle touchstone
files, and there's been a number of little bugfixes.
As ever, I look forward to hearing what bugs you find, and what new
features you want! :-)
--
Rune / 5Q5R
On Wed, 18 Sep 2019 at 18:05, hwalker <herbwalker2476@...> wrote:
Rune,
The new "Using the software" section on your GitHub page (
) is much appreciated! The
new pip installation also is nice, although on Windows I prefer to
just download your release and run the executable from my "C:\NanoVNA" directory.
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Re: Finger tightening SMA connections
If you get the "thin sma spanner tool" at like 3-4 GBP from sdr-kits, and
you have a dynamometer capable of measuring 6N accurately, you can actually
get a fairly accurate .3 Nm pulling at the tiny hole with the spanner
attached to an SMA collar nut, the spanner as vertical as possible and
pulling the dynamometer horizontally.
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Oristo
F4WCV
Kurt Poulsen