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I am building different Un:Uns using different wiring schemes and caps. While testing a config, I noticed that my battery was down to one bar and I did not have the USB cable plugged in at the time. I was not keeping records at the time, just quick tests. So I did not have my nanovna H4 4.3 plugged in, not using Nanovna-App at the time. I just plugged it in and saw the plot change on the nano display. I went HMMMM. was i touching something? did I move something? No.
I started testing by unplugging the usb, and my original plot came back. Then I plugged it back in and back to same "changed" plot. Repeatable and always the same places the changed occurred.
Thought, maybe my cable is bad. Nope tried 3 different higher quality cables and exact same results. Did the same test on PC directly and not on the usb expansion bar (maybe it introduces the problem). Nope, same plot changes on pc directly to nanovna with all 3 cables. OK, maybe some ferrites will help. Put on 2 Fair-rite type 31 beads (purchased from Mouser, not amazon or ebay!), same changes.
ok remove pc from the equation... I tested on a laptop with battery only, no outside electricity. Desktop on laptop has no apps open (nanovna-app) or anything. Simply plugging in the usb cable changes the plot on the nanovna, not the same but very similar change to the pc plugged in change.
I also let the nanovna FULLY charge while turned off and then tested again. Simply plugging into an external power source via the usb is causing the issue.
Has anyone seen this before? Do you think that the battery charging circuit in the vna is causing the issue (before I examine this further)?
Some details about the nanovna. Nanovna H4. HW version 4.3_MS
It was purchased via Amazon from the AURSINC store, which was listed on the nanovna.com site as a authentic seller.
I have looked inside the unit and it is clean and well manufactured. Clean solder points and the unit arrived in the official box with all parts.
I believe this to be an authentic unit and not clone.
The errors are shown across the whole spectrum but are very low at low frequencies and grow exponentially higher with higher frequencies. I am doing a S21 logmag plot from 1MHz to 30MHz. There also seems to be large shift (jump down) around 15MHz.
Any thoughts would be welcomed.
Thanks in advance,
Mark
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I¡¯ve seen similar as well. Oftentimes I don¡¯t take the time to test with multiple configurations but occasionally I¡¯ve noticed where either the Smith chart trace ¡°doesn¡¯t look right¡± or the SWR plot, and that leads me to a bad connector, etcetera. Even holding the NanoVNA or having a laptop too close changed things, so not too surprised that adding a USB cable had that effect. It¡¯s certainly not a laboratory-grade instrument but it does very well for what it costs¡. Does recalibrating help at all? That would be my first instinct but I¡¯m curious to try it myself now.
73, Greg
KN7GIG
"Silence is golden. Duct tape is silver."
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On Aug 27, 2023, at 21:56, Mark KQ4EKK <kq4ekk+groups@...> wrote:
?I am building different Un:Uns using different wiring schemes and caps. While testing a config, I noticed that my battery was down to one bar and I did not have the USB cable plugged in at the time. I was not keeping records at the time, just quick tests. So I did not have my nanovna H4 4.3 plugged in, not using Nanovna-App at the time. I just plugged it in and saw the plot change on the nano display. I went HMMMM. was i touching something? did I move something? No.
I started testing by unplugging the usb, and my original plot came back. Then I plugged it back in and back to same "changed" plot. Repeatable and always the same places the changed occurred.
Thought, maybe my cable is bad. Nope tried 3 different higher quality cables and exact same results. Did the same test on PC directly and not on the usb expansion bar (maybe it introduces the problem). Nope, same plot changes on pc directly to nanovna with all 3 cables. OK, maybe some ferrites will help. Put on 2 Fair-rite type 31 beads (purchased from Mouser, not amazon or ebay!), same changes.
ok remove pc from the equation... I tested on a laptop with battery only, no outside electricity. Desktop on laptop has no apps open (nanovna-app) or anything. Simply plugging in the usb cable changes the plot on the nanovna, not the same but very similar change to the pc plugged in change.
I also let the nanovna FULLY charge while turned off and then tested again. Simply plugging into an external power source via the usb is causing the issue.
Has anyone seen this before? Do you think that the battery charging circuit in the vna is causing the issue (before I examine this further)?
Some details about the nanovna. Nanovna H4. HW version 4.3_MS
It was purchased via Amazon from the AURSINC store, which was listed on the nanovna.com site as a authentic seller.
I have looked inside the unit and it is clean and well manufactured. Clean solder points and the unit arrived in the official box with all parts.
I believe this to be an authentic unit and not clone.
The errors are shown across the whole spectrum but are very low at low frequencies and grow exponentially higher with higher frequencies. I am doing a S21 logmag plot from 1MHz to 30MHz. There also seems to be large shift (jump down) around 15MHz.
Any thoughts would be welcomed.
Thanks in advance,
Mark
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Hello
I just did a test on mine which is a NanoVNA-F [v1.0.5]
Is it real? a clone ? I bought it in February 2021 : Moligh doll Vector Network Analyzer NanoVNA-F HF VHF UHF UV VNA Antenna Analyzer 10KHz-1.5GHz 4.3 Inch Press Screen
Sold by : Amazon
hui zhou shi hong qing dian zi you xian gong si
hui yang qu dan shui kai cheng da dao bei
17 hao er lou si shi qi ka wei
hui zhou shi, GUANG DONG SHENG, 516211
CN
-----------------------
It was connected to a 5 m coaxial cable with a line cap "in the air" at the end (I calibrated before at the end of the cable). When I plugged the USB plug into my PC, without launching nanaovna-saver, the figure displayed did not change; the NanoVNA is in permanent scanning (relaxed).
I tried with a real antenna, at the end of an additional 10 m cable but earthed at the bottom; same, nothing changed.
On the other hand, if when I plug in the USB plug nothing happens, when I unplug the plug, it's like when I turn on the NanoVNA, with the home page displayed briefly. The same figure reappears on the screen as before unplugging.
73
--
F1AMM
Fran?ois
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On Sun, Aug 27, 2023 at 09:56 PM, Mark KQ4EKK wrote:
I am building different Un:Uns using different wiring schemes and caps.
It sounds as if your measurement system is not sufficiently decoupling the test articles, so the test system is becoming part of the measurement; this happens often when measuring antennas. Perhaps if you shared a diagram of your test system it would help us to understand what is going on. Since you are testing ununs, it is possible that one of your measurement ports has a floating shield connection or similar, which picks up a ground (sorta) when the USB cable is plugged in. 73, Don N2VGU
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Thanks to all for their help with this.
Greg, it is not a bad connector, I changed and tested all connection points, cables, etc. with identical and test units in order to remove those variables. I always recalibrate for each set of tests. I have removed all outside interference possibilities that I can. I do not move anything near the unit, dont touch anything and just take notes on readings. I attached two pics. One with USB and one without, you can see the changes clearly. The test rig is 2 identical built unun (haha, well as much as possible) in a back to back configuration. The secondaries are connected and the the ground legs are connected. The test is S21 thru displaying Smith and logmag. I am able to wave hands over everything with no change, only when I touch something with a fingertip do I see changes (of course). But it is overall stable. When USB is connected it changes as indicated on pics. It is not variable unless I change the usb source (laptop vs pc vs charger etc). As you said, not a laboratory-grade instrument. Understood. I have not tested anything other circuits yet, only my current unun config since I noticed this, but I will shortly to see if it happens during other test and scales. I just wanted to understand if anyone is seeing this. Not concerned to much yet, but I usually do testing with the PC apps when working on bench and worried that I may have gotten errors in my old stuff worked on.
Francious, good to know. I may just be running a sensitive test and I am hunting efficiency, so I am looking closely and these number changes and they reflect a lot of change in overall result.
Donald, the test system hopping in could be quite possible. I am testing the wire wrapped toroids with wires only into screw terminals to bnc and nanovna.. I am sure the connections are all good and solid while not optimum. I was testing many configs to search for best results in turns and caps and toroid materials. Then I noticed the changes in traces and stopped testing in search of the problem (error introductions). I just want to make sure that this is small issue and not a power circuit problem with my unit or a possible issue in the design of the power/charging system introducing these errors. And how I can isolate my usb connection further.
thanks all!!
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How many times do we, collectively, need to point out that EXTENDING THE
COUNTERPOISE WILL CHANGE READINGS?
Attaching the USB cable is lengthening the extent of the counterpise from
just the NANOVNA to NANOVNA PLUS USB cable. Of course the reading will not
agree!
Dave - W?LEV
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On Mon, Aug 28, 2023 at 5:07?PM Mark KQ4EKK <kq4ekk+groups@...> wrote: Thanks to all for their help with this.
Greg, it is not a bad connector, I changed and tested all connection
points, cables, etc. with identical and test units in order to remove those
variables. I always recalibrate for each set of tests. I have removed all
outside interference possibilities that I can. I do not move anything
near the unit, dont touch anything and just take notes on readings. I
attached two pics. One with USB and one without, you can see the changes
clearly. The test rig is 2 identical built unun (haha, well as much as
possible) in a back to back configuration. The secondaries are connected
and the the ground legs are connected. The test is S21 thru displaying
Smith and logmag. I am able to wave hands over everything with no change,
only when I touch something with a fingertip do I see changes (of course).
But it is overall stable. When USB is connected it changes as indicated on
pics. It is not variable unless I change the usb source (laptop vs pc vs
charger etc). As you said, not a laboratory-grade instrument.
Understood. I have not tested anything other circuits yet, only my current
unun config since I noticed this, but I will shortly to see if it happens
during other test and scales. I just wanted to understand if anyone is
seeing this. Not concerned to much yet, but I usually do testing with the
PC apps when working on bench and worried that I may have gotten errors in
my old stuff worked on.
Francious, good to know. I may just be running a sensitive test and I am
hunting efficiency, so I am looking closely and these number changes and
they reflect a lot of change in overall result.
Donald, the test system hopping in could be quite possible. I am testing
the wire wrapped toroids with wires only into screw terminals to bnc and
nanovna.. I am sure the connections are all good and solid while not
optimum. I was testing many configs to search for best results in turns
and caps and toroid materials. Then I noticed the changes in traces and
stopped testing in search of the problem (error introductions). I just
want to make sure that this is small issue and not a power circuit problem
with my unit or a possible issue in the design of the power/charging system
introducing these errors. And how I can isolate my usb connection further.
thanks all!!
-- *Dave - W?LEV*
--
Dave - W?LEV
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An essential principle of troubleshooting is to be able to reproduce the phenomenon. As long as another operator has not been able to contater the same thing as KQ4EKK, all the various and varied explanations are doomed to failure.
I tried the tests on my nanoVNA-F and my PC in my environment, nothing happens. Unfortunately, that doesn't prove anything. It's a negative test.
It can come:
Of the environment
- NanoVNA itself, and this one only (failure)
- cord
- of a procedure
- Basically anything.
I had to troubleshoot magical phenomena. We must already convince ourselves that there is an explanation for that. What is positive in what Marc relates is that at home, on his table, the phenomenon is stable. Perhaps you should describe your environment more precisely.
Can you do a much lower frequency test, between 10 and 50 MHz for example. A simple piece of coax in a closed circuit at the end, for example. I see on your images that you sweep from 1.5 GHz to 30 Ghz and it is in the very high frequencies that the difference appears. My tests were not at all in this frequency band
You state: Errors are displayed across the spectrum but are very small at low frequencies and increase exponentially with higher frequencies. I'm doing an S21 logmag plot from 1 MHz to 30 MHz. There also seems to be a significant offset (jump down) around 15 MHz.
We should focus on this type of experience
--
F1AMM
Fran?ois
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Yes, I understand. My test are in the MHz not GHz. That is a period and not a comma, but yes I get your point. Will do.
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Already understood and thanks. Maybe a better question is: Is there a method to isolate the VNA from the PC when connected via the USB to kill (choke?) the effect. I am just experimenting and learning here, by no means am I a veteran on vna usage.
Thanks Dave.
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Connect the VNA over Bluetooth serial. You can buy the adapters for a few $.
How to attach the adapter has been discussed a number of times here.
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On Mon, 28 Aug 2023 at 21:51, Mark KQ4EKK <kq4ekk+groups@...> wrote:
Already understood and thanks. Maybe a better question is: Is there a method to isolate the VNA from the PC when connected via the USB to kill (choke?) the effect. I am just experimenting and learning here, by no means am I a veteran on vna usage.
Thanks Dave.
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Hi Mark-
What's causing the data to change when you plug the unit into the USB cable is the fact that adding the USB connection causes that USB cable (and whatever else it's connected to) to become part of the antenna system. Therefore, the impedance that the network analyzer is looking into has actually changed.
That's why battery operation is such a nice thing! :-)
Tom
AE5I
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Unbalanced antenna should have sufficiently large ground plane to minimize impact of transmission line. Objects near the antenna can change characteristics of the antenna. Such as people and things in a room that act on radio waves at the frequency under test. Some people recommend consideration of objects within ten wavelengths for their impact.
There's a good chance many VNA lab experiments do not fully account for environmental impact on antennas. VHF antennas may be too large to correctly build indoors, and UHF or higher antennas may not be constructed with enough precision to truly evaluate the design. Commercially, antennas are range tested and can be measured when installed at the customer location. VHF range testing means a lot of land. Customer's on-site measurements should be made and reviewed carefully.
The other thread discusses balanced antenna measurement.
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Hello Mark,
I do not pretend to be an expert here, but I will make a few observations.
1. Many posts in this group have already noted that connecting a NanoVNA to a computer via USB cable results in an effective counterpoise being created which will change the tuning of the system under test.
2. Most professional VNAs are mains powered so you can not do a "battery vs USB" measurement comparison. Nothing to do with "laboratory grade" equipment.
3. Even professional grade battery operated VNAs have significant physical "bulk" compared to a NanoVNA so measurements will be disturbed less than those of the physically smaller sized NanoVNA.
4. Try measuring a 2M or 70cm hand held radio antenna fitted directly to the S11 port. Do the measurement holding the NanoVNA in your hand and with the NanoVNA sitting on a large cardboard box. You will notice a significant difference due to your body affecting the measurement.
So all I can suggest is fitting a ferrite to your USB cable to decouple it. Wind several turns through a large ferrite tube or toroid. Maybe one at each end.
I would suggest type 43 ferrite, but please, anyone with more knowledge here, please step in.
The main thing is you need to try to "kill" the counterpoise effect created by your USB cable.
HTH...Bob VK2ZRE
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On 29/08/2023 3:07 am, Mark KQ4EKK wrote: Thanks to all for their help with this.
Greg, it is not a bad connector, I changed and tested all connection points, cables, etc. with identical and test units in order to remove those variables. I always recalibrate for each set of tests. I have removed all outside interference possibilities that I can. I do not move anything near the unit, dont touch anything and just take notes on readings. I attached two pics. One with USB and one without, you can see the changes clearly. The test rig is 2 identical built unun (haha, well as much as possible) in a back to back configuration. The secondaries are connected and the the ground legs are connected. The test is S21 thru displaying Smith and logmag. I am able to wave hands over everything with no change, only when I touch something with a fingertip do I see changes (of course). But it is overall stable. When USB is connected it changes as indicated on pics. It is not variable unless I change the usb source (laptop vs pc vs charger etc). As you said, not a laboratory-grade instrument. Understood. I have not tested anything other circuits yet, only my current unun config since I noticed this, but I will shortly to see if it happens during other test and scales. I just wanted to understand if anyone is seeing this. Not concerned to much yet, but I usually do testing with the PC apps when working on bench and worried that I may have gotten errors in my old stuff worked on.
Francious, good to know. I may just be running a sensitive test and I am hunting efficiency, so I am looking closely and these number changes and they reflect a lot of change in overall result.
Donald, the test system hopping in could be quite possible. I am testing the wire wrapped toroids with wires only into screw terminals to bnc and nanovna.. I am sure the connections are all good and solid while not optimum. I was testing many configs to search for best results in turns and caps and toroid materials. Then I noticed the changes in traces and stopped testing in search of the problem (error introductions). I just want to make sure that this is small issue and not a power circuit problem with my unit or a possible issue in the design of the power/charging system introducing these errors. And how I can isolate my usb connection further.
thanks all!!
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Back in the 70's I worked for GE testing yokes on TV's. The yokes had a couple of layers of #22 enameled wire etc... I say all this to open some ideas or complaints regarding using these yokes to do the decoupling of the USB? cable, just thinking..... (I was a technician)
Mike C. Sand Mtn GA
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On 8/29/2023 3:36 AM, Bob Ecclestone VK2ZRE wrote: Hello Mark,
I do not pretend to be an expert here, but I will make a few observations.
1. Many posts in this group have already noted that connecting a NanoVNA to a computer via USB cable results in an effective counterpoise being created which will change the tuning of the system under test.
2. Most professional VNAs are mains powered so you can not do a "battery vs USB" measurement comparison. Nothing to do with "laboratory grade" equipment.
3. Even professional grade battery operated VNAs have significant physical "bulk" compared to a NanoVNA so measurements will be disturbed less than those of the physically smaller sized NanoVNA.
4. Try measuring a 2M or 70cm hand held radio antenna fitted directly to the S11 port. Do the measurement holding the NanoVNA in your hand and with the NanoVNA sitting on a large cardboard box. You will notice a significant difference due to your body affecting the measurement.
So all I can suggest is fitting a ferrite to your USB cable to decouple it. Wind several turns through a large ferrite tube or toroid. Maybe one at each end.
I would suggest type 43 ferrite, but please, anyone with more knowledge here, please step in.
The main thing is you need to try to "kill" the counterpoise effect created by your USB cable.
HTH...Bob VK2ZRE
On 29/08/2023 3:07 am, Mark KQ4EKK wrote:
Thanks to all for their help with this.
Greg, it is not a bad connector,? I changed and tested all connection points, cables, etc. with identical and test units in order to remove those variables.? I always recalibrate for each set of tests.? I have removed all outside interference possibilities that I can.? I do not move anything near the unit, dont touch anything and just take notes on readings.? I attached two pics.? One with USB and one without, you can see the changes clearly.? The test rig is 2 identical built unun (haha, well as much as possible) in a back to back configuration.? The secondaries are connected and the the ground legs are connected.? The test is S21 thru displaying Smith and logmag.? I am able to wave hands over everything with no change, only when I touch something with a fingertip do I see changes (of course).? But it is overall stable.? When USB is connected it changes as indicated on pics.? It is not variable unless I change the usb source (laptop vs pc vs charger etc).? As you said, not a laboratory-grade instrument.? Understood.? I have not tested anything other circuits yet, only my current unun config since I noticed this, but I will shortly to see if it happens during other test and scales.? I just wanted to understand if anyone is seeing this.? Not concerned to much yet, but I usually do testing with the PC apps when working on bench and worried that I may have gotten errors in my old stuff worked on.
Francious, good to know.? I may just be running a sensitive test and I am hunting efficiency, so I am looking closely and these number changes and they reflect a lot of change in overall result.
Donald,? the test system hopping in could be quite possible.? I am testing the wire wrapped toroids with wires only into screw terminals to bnc and nanovna.. I am sure the connections are all good and solid while not optimum.? I was testing many configs to search for best results in turns and caps and toroid materials. Then I noticed the changes in traces and stopped testing in search of the problem (error introductions).? I just want to make sure that this is small issue and not a power circuit problem with my unit or a possible issue in the design of the power/charging system introducing these errors.? And how I can isolate my usb connection further.
thanks all!!
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Donald S Brant Jr
Mike C.