Re: USB vs no USB readings Plots change...
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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Re: How do you measure a car antenna?
Well, some of them kind of do.? ? ?Part of Dynamic Braking!
Kent
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On Wednesday, August 30, 2023 at 09:14:21 AM CDT, Mike C. <mg@...> wrote: EV's don't have "alternators". :0) On 8/27/2023 5:52 PM, Rick Murphy wrote: The AM radio in my car works just fine. Chevy BoltEV.
How short our memories are - does nobody else remember "alternator noise"?
Cars are mobile noise generators.
73,
? ? ? -Rick
On Sat, Aug 26, 2023 at 9:47?PM N7RWB Craig Cherry via groups.io
<craig.cherry@...>? wrote:
Ken, looking through FCC part 15 rules on emissions, I don¡¯t see any
exemption for electric car motors or power systems. Do you have a reference
to a FCC document for the exemption you mentioned?
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Re: Not available at Ali Express / Zeenko
Randl.com is where I got my H4.
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On Wed, Aug 30, 2023, 09:24 KD2YYI <tim.sooley@...> wrote: As someone who just got nanoVNA 4 from amazon I recommend following this
guide from nanovna.com to ensure you get a legit one that is firmware
upgradable.
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Re: How do you measure a car antenna?
EV's don't have "alternators". :0)
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On 8/27/2023 5:52 PM, Rick Murphy wrote: The AM radio in my car works just fine. Chevy BoltEV.
How short our memories are - does nobody else remember "alternator noise"?
Cars are mobile noise generators.
73,
-Rick
On Sat, Aug 26, 2023 at 9:47?PM N7RWB Craig Cherry via groups.io
<craig.cherry@...> wrote:
Ken, looking through FCC part 15 rules on emissions, I don¡¯t see any
exemption for electric car motors or power systems. Do you have a reference
to a FCC document for the exemption you mentioned?
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Re: Not available at Ali Express / Zeenko
As someone who just got nanoVNA 4 from amazon I recommend following this guide from nanovna.com to ensure you get a legit one that is firmware upgradable.
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Re: Not available at Ali Express / Zeenko
I THINK you can buy the nano VNA 4 on Amazon.
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Re: nano VNA-H will not connect via USB to control apps on Win10 - help please
Hi Paul
There are no devices shown in gray. nanoVNA-QT can't see the device. Instructions in say it needs a driver. I installed CypressDriverInstaller_1.exe
Still doesn't work.
Thanks
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Re: nano VNA-H will not connect via USB to control apps on Win10 - help please
Hi Steve
yes, I have 4 cables, all check good using other devices
Thanks
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Re: nano VNA-H will not connect via USB to control apps on Win10 - help please
Hi Brian,
Have you tried a different USB cable?? I use the same cable that I use with my Android cell phone and it works perfectly.? I use Win 10 and I never had to install different drivers... NanoVNA connected right out of the box.? I'm not saying that this will absolutely solve your problem, but sometimes we jump to the conclusion that the problem is much more complicated and difficult than it actually is...? ; )
Good Luck!
Steve N0GWC
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On 8/29/23 8:32 PM, Brian Stokes wrote: I posted this query on Jul 17 #33483
There were no helpful replies.
I have tried installing every USB driver I can find for the nanoVNA but none of them makes the nanoVNA appear in the list of USB devices.
Have installed Cypress driver and 64 bit ST virtual COM port app.
No new COM ports appear when VNA is connected nor when virtual COM port app installed.
Device manager shows new 'Unknown USB device (device descriptor request failed)' when VNA-H is connected and powered up. Cable appears to be good since Device manager sees the VNA.
Tried several apps, VNA-QT, nanoVNA sharp 1.03, nanoVNAsaver, none will connect.
PC is Win 10.
Thanks for your help.
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Re: nano VNA-H will not connect via USB to control apps on Win10 - help please
I don't think you need to add any drivers on Win 10... (Pretty sure, I didn't, anyway. But it's been quite a while.)
You might try going into Device Manager, select View / Show Hidden Devices, and remove the hidden COM devices (they'll be shown in gray.) Disconnect your nanoVNA first...
You could even watch devices and you plugin your nanoVNA, and see what's actually going on. (It actually starts as a USB device, and the driver makes it into a COM device.)
Paul
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On 8/29/23 18:32, Brian Stokes wrote: I posted this query on Jul 17 #33483
There were no helpful replies.
I have tried installing every USB driver I can find for the nanoVNA but none of them makes the nanoVNA appear in the list of USB devices.
Have installed Cypress driver and 64 bit ST virtual COM port app.
No new COM ports appear when VNA is connected nor when virtual COM port app installed.
Device manager shows new 'Unknown USB device (device descriptor request failed)' when VNA-H is connected and powered up. Cable appears to be good since Device manager sees the VNA.
Tried several apps, VNA-QT, nanoVNA sharp 1.03, nanoVNAsaver, none will connect.
PC is Win 10.
Thanks for your help.
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nano VNA-H will not connect via USB to control apps on Win10 - help please
I posted this query on Jul 17 #33483
There were no helpful replies.
I have tried installing every USB driver I can find for the nanoVNA but none of them makes the nanoVNA appear in the list of USB devices.
Have installed Cypress driver and 64 bit ST virtual COM port app.
No new COM ports appear when VNA is connected nor when virtual COM port app installed.
Device manager shows new 'Unknown USB device (device descriptor request failed)' when VNA-H is connected and powered up. Cable appears to be good since Device manager sees the VNA.
Tried several apps, VNA-QT, nanoVNA sharp 1.03, nanoVNAsaver, none will connect.
PC is Win 10.
Thanks for your help.
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
For large, high-Q coils, some crystal set builders use a styrofoam cake dummy like this:
Styrofoam is as close to air as anything solid I know of. It may be tedious to set up, but if you can support whatever you're measuring with fishing line you should be able to eliminate all support interaction. But you still have to worry about other stuff in the room. One time I was trying to accurately measure the Q of a large coil with my HP 4342A Q meter. I was astounded to find that I had to remove myself several feet and crouch down to eliminate interaction with my body. Even then I wasn't sure I got rid of it all. I couldn't read the meter from any farther away.
Brian
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
On 8/29/23 1:55 PM, W0LEV wrote: Large styrofoam blocks are the "standard" in professional communities. At
home, with all the RF test equipment, I use either corrugated boxes or an
empty 50-gallon rubbish can. I could buy large styrofoam blocks from Hobby
Lobby (at least they used to carry them), but I'd have trouble storing them
with wifie.
We use blocks covered with static dissipative film (Amstat, etc.) The surface resistance is sufficiently high that it doesn't load the RF system, but it also prevents the charge that inevitably accumulates on foam from destroying your electronics.
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
Large styrofoam blocks are the "standard" in professional communities. At
home, with all the RF test equipment, I use either corrugated boxes or an
empty 50-gallon rubbish can. I could buy large styrofoam blocks from Hobby
Lobby (at least they used to carry them), but I'd have trouble storing them
with wifie.
Dave - W?LEV
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On Tue, Aug 29, 2023 at 7:56?PM Brian Beezley <k6sti@...> wrote: Corrugation should lower the dielectric constant and loss of any material
roughly in proportion to its air content. So corrugated cardboard should
have better specs than the uncorrugated cardboard specs I quoted. However,
the electric field of the object under test will be maximum where it
touches the support. It's there where the dielectric properties of the
support matter. Increasing the size of a supporting box is unlikely to
reduce the effect of lossy box material.
Using lossy materials with high dielectric constant is fine for casual
measurements. But it pays to use something more transparent to electric
fields when the measurement is important. This also applies to the magnetic
field. Avoid anything ferromagnetic or conductive nearby.
Brian
-- *Dave - W?LEV*
--
Dave - W?LEV
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
Corrugation should lower the dielectric constant and loss of any material roughly in proportion to its air content. So corrugated cardboard should have better specs than the uncorrugated cardboard specs I quoted. However, the electric field of the object under test will be maximum where it touches the support. It's there where the dielectric properties of the support matter. Increasing the size of a supporting box is unlikely to reduce the effect of lossy box material.
Using lossy materials with high dielectric constant is fine for casual measurements. But it pays to use something more transparent to electric fields when the measurement is important. This also applies to the magnetic field. Avoid anything ferromagnetic or conductive nearby.
Brian
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
One can easily MEASURE the ¦År of the corrugated box material. Build a parallel plate capacitor using aluminum foil, single or double-sided FR-4 PCB, or some other creative set of flat conductors. Measure the capacitance using the NANOVNA (Smith Chart) with only air between the plates. Then slip in and fill the volume between the plates with your unknown material. Again measure the capacitance. Since the capacitance is a linear function of ¦År, the ¦År of the unknown material is the ratio of the two measurements, unknown over air measurements of the two capacitances. What's more, you can measure the ¦År as a function of frequency as well. Dave - W?LEV On Tue, Aug 29, 2023 at 7:23?PM W0LEV via groups.io <davearea51a= [email protected]> wrote: Possibly the ¦År rating of the corrugated paper, itself, is well above
unity, which I seriously doubt. But a large box is pretty much all air
with an ¦År miniscually larger than unity.
Dave - W?LEV
On Tue, Aug 29, 2023 at 7:03?PM Brian Beezley <k6sti@...> wrote:
On Tue, Aug 29, 2023 at 11:41 AM, W0LEV wrote:
Dry discarded corrogated shipping boxes also work well.
I used to use cardboard to support things until I found these 1 MHz specs
for cardboard with a density 0.5 ounces per cubic inch: dielectric constant
6, loss tangent 0.04. By contrast, styrofoam type 103.7 has a dielectric
constant of 1.03 and a loss tangent of 0.000021. At 3 GHz the loss tangent
is 0.0001.
Brian
--
*Dave - W?LEV*
--
Dave - W?LEV
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
Possibly the ¦År rating of the corrugated paper, itself, is well above
unity, which I seriously doubt. But a large box is pretty much all air
with an ¦År miniscually larger than unity.
Dave - W?LEV
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On Tue, Aug 29, 2023 at 7:03?PM Brian Beezley <k6sti@...> wrote: On Tue, Aug 29, 2023 at 11:41 AM, W0LEV wrote:
Dry discarded corrogated shipping boxes also work well.
I used to use cardboard to support things until I found these 1 MHz specs
for cardboard with a density 0.5 ounces per cubic inch: dielectric constant
6, loss tangent 0.04. By contrast, styrofoam type 103.7 has a dielectric
constant of 1.03 and a loss tangent of 0.000021. At 3 GHz the loss tangent
is 0.0001.
Brian
-- *Dave - W?LEV*
--
Dave - W?LEV
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Re: NanoVNA for 120 ohm Twin wire Balanced lines
On Tue, Aug 29, 2023 at 11:41 AM, W0LEV wrote:
Dry discarded corrogated shipping boxes also work well.
I used to use cardboard to support things until I found these 1 MHz specs for cardboard with a density 0.5 ounces per cubic inch: dielectric constant 6, loss tangent 0.04. By contrast, styrofoam type 103.7 has a dielectric constant of 1.03 and a loss tangent of 0.000021. At 3 GHz the loss tangent is 0.0001. Brian
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When I worked on GPS initial design we had a rigorous spec for the noise
temperature of several of the receivers. This was in the late 1970's. We
could not make the spec with anything from the US at the time but could
using an NEC part from Japan. At the time this was a national security
issue with the fear of "hijacked' devices from the Soviet Union or
elsewhere with unwanted "codes" embedded in them. This was WELL before the
present-day fakes so common from China. We ultimately had to get a letter
from the Pentagon, yes, the Pentagon (!!), to use the NEC part. I saw the
letter.
Be glad this issue is just political and not linked to national security.
Dave - W?LEV
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On Tue, Aug 29, 2023 at 6:38?PM Jim Lux <jimlux@...> wrote: On 8/28/23 11:23 AM, drfuka@... wrote:
Howdy,
Are there any US Manufacturers building/selling NanoVNAs? I am on a project that is regulated by The Build America Buy America Act and NDAA889
Laws which unfortunately make the linked purchase options not possible.
Related question: I would like to give someone who is BABAA/NDAA889 compliant a project to build a custom software-only version without the
display, LY-K3-01B switch, battery, USBC, Charge circuit, ... basically
just a software NanoVNA-H for a project I am working on. I am checking with
SparkFun, but is there anyone in the friends and family of this amazing
project that might be interested, and if so, about how much would it cost
for US-made boards?
The Buy American Act probably falls in the exception:
"the items to be procured or the materials from which they are
manufactured must be present in the United States in sufficient and
reasonably available commercial quantities of a satisfactory quality.
The provisions of the act may be waived if the head of the procuring
agency determines the act to be inconsistent with the public interest or
the cost of acquiring the domestic product is unreasonable. "
The items to be procured aren't present in the US. In my government
funded job, we buy things from foreign mfrs all the time: Think
Rhode+Schwarz test equipment, SpaceWire test equipment, or even more
mundane, fancy RF cables.
Yes, you have to fill out a form saying why you can't get it from a
domestic supplier.
NDAA889 is potentially more troubling, but I think it covers only
"Telecommunications Equipment and Services" and the NanoVNA doesn't fall
into that bucket.
-- *Dave - W?LEV*
--
Dave - W?LEV
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I was just speaking with a fellow who does such work and, unsurprisingly, his first question to me was "How many initially and per year and what is the budget?".
It might wind up cheaper renting a Keysight/Anritsu/Copper Mountain commercial unit once all of the qualified vendor paperwork (which is also not free) gets settled. Of course none of them are made in USA either.
73, Don N2VGU
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Mike C.
Paul - AI7JR
Donald S Brant Jr