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On Fri, Jul 8, 2022 at 03:07 PM, <jetmech@...> wrote:

I purchased a NanoVNA off of Amazon. Seem to work when I got it, but then
when I tried to calibrate it I'm able to. I even tried updating the firmware.
I exchanged it for another one and this time It will not calibrate at all. I
tried using the RF Demo kit as well. I got the -H, but the RF Demo kit says
its for the -F, did I kill the NanoVNA using the -F RF Demo kit?

The replacement when using the smith chart doesn't move from center even with
open or shorted cap.

There is no problem using the RF Demo kit with any NanoVNA.

If you are having calibration problems check the cal loads with a DMM to make sure you have an open, load and short. Calibrate right on the NanoVNA and only use the cable for the through cal.

When doing a cal make sure your RESET the calibration before you start and SAVE to one of the slots when done. After cal check with your loads on the Smith chart. Short on far left, 50 ohm in middle and open on far right.

Roger

On Sat, Jul 9, 2022 at 09:36 AM, Mike Millen wrote:

I think you'll find if you leave that black window a bit longer, then
NanoVNA will load... it's a slow starter, that's all.

NanoVNA Saver was written in python and all the necessary files to run are "packaged" in the .exe file. Each one is scanned by the virus scanner and it takes a long time to load because of this. On slower machines the "black window" will be there for 15 to 20 seconds before the Saver screen appears.

Roger

I think you'll find if you leave that black window a bit longer, then NanoVNA will load... it's a slow starter, that's all.

Mike

I mostly use the box alone. NanoVNA-saver refuses to run on my PC (Win10pro, just gives a black window). I have tried VNA-qt, and the big screen is nice, but -qt lacks some features available on the box itself. Is there a more powerful client I should try, or help getting -saver to function?

My nanoVNA is also from Amazon but it's a nanoVNA-F. I did not sound the difference with your -H.

Using the box alone is crazy. I advise you to use it through nanovna-saver. It's a bit of a hassle to connect the COM port via USB, but then it's a joy. The calibrations are done from nanovna-saver and you will no longer have to touch the box (except for the connecting straps, of course).
--
F1Amm Fran?ois

There is no difference in calabration kits except maybe different connectors.
Clyde KC7BJE

Respectfully, I think measuring a CM choke is being overly complicated in this discussion. The common mode Z is measured just as if the CM choke was an inductor or capacitor. Either measure it with an S11 measurement (shield to shield leaving the center conductor alone or short the input terminals and output terminals together) across Port 0 or do an S21 Thru method getting the insertion loss and the phase angle (input shield to port 0 center conductor and output shield to port 1 center conductor leaving the center conductor of the coax alone. If bifilar-wound, short the input terminals together at port 0 and the output terminals together at port 1 OR determine which conductor is common to in and out and use that conductor only).
If it is necessary to use port 0 and 1 to measure insertion loss just do an S21 with the CM choke connected as if the core wasn't there as the core is immaterial for a CM choke's loss (not so for a bifilar-wound CM choke because Zo is not well controlled so there will be loss due to mismatch).
73

Remember when doing a new calibration, you FIRST must *clear* BEFORE
running the new calibration.

I can not imagine two units behaving identically in this respect.

Dave - W?LEV

--
Dave - W?LEV

I purchased a NanoVNA off of Amazon. Seem to work when I got it, but then when I tried to calibrate it I'm able to. I even tried updating the firmware. I exchanged it for another one and this time It will not calibrate at all. I tried using the RF Demo kit as well. I got the -H, but the RF Demo kit says its for the -F, did I kill the NanoVNA using the -F RF Demo kit?

The replacement when using the smith chart doesn't move from center even with open or shorted cap.

FWIW I know .001% of what I'm doing.

Hello Ed,

To measure the differential mode performance, the windings must be wired
in series and provide an anti-phase arrangement - that is winding 1 end is
joined to winding 2 end and nano VNA connections are channel 0 & channel 1
to winding 1 start and winding 2 start.

I have not seen this configuration before (I use the configuration
mentioned here: ).
Any link to an article about this way of measuring DM?

All the best,

Victor

The diagram from Miro F9LR is very generalized.

It is not specific for the case where the DUT is a common mode current choke (current balun).

It might be helpful to review what a common mode choke is to establish how to correctly connect it to a nanoVNA.

A common mode choke is a transformer having two seperate, isolated windings, each having a start point and an endpoint. It is intended for use in a balanced transmission line.

The nanoVNA channels are 'unbalanced' and share a common (cold) connection.

The common mode choke has 4 wires or terminals, these must be connected correctly to configure it as the DUT. The wiring arrangement is different for measuring thru performance of the common mode signal and the differential mode signal.

The 4 wires, I will call winding 1 start, winding 1 end, winding 2 start and winding 2 end.

Now the common signal means that the same signal must be applied to both windings in the same orientation or polarity. Therefore winding 1 start must be connected to winding 2 start and winding 1 end connected to winding 2 end.

Respectively, the joined wires or terminals are connected to nanoVNA channel 0 and channel 1, to measure the common mode performance.

To measure the differential mode performance, the windings must be wired in series and provide an anti-phase arrangement - that is winding 1 end is joined to winding 2 end and nano VNA connections are channel 0 & channel 1 to winding 1 start and winding 2 start.

I hope that helps

Ed G8FAX

Hello Francois,

I made an error (this was highlighted to me by a fellow list reader):
everywhere I use: mu' + jmu", should have been mu' - jmu"

All the best,

Victor


Op di 5 jul. 2022 om 23:13 schreef Victor Reijs via groups.io
<pe1atn.victor.reijs@...>:

Well.. you already see the multifunction capability (Spectrum Analyzer, 1 direction VNA) in popular instruments like the Keysight Fieldfox, and similar devices from Anritsu, etc.

There will always be a market for single purpose devices - highly cost (or size/weight/power) constrained applications where you don't want to spend the extra pennies for the components; and where you need the ultimate in measurement performance. It's like counters and spectrum analyzers - both can measure the frequency of a signal, but they tend to have different reference oscillators (ADEV vs Phase Noise optimization) and because they use different measurement techniques, they are optimized for particular applications. Another example might be precision measurement of RF power - a broadband calorimetric power meter or a narrow band filter with a detector (what a spectrum analyzer is). Getting 0.5% accuracy from a broadband power meter is straightforward, getting 0.1% uncertainty is difficult, but possible. I don't think there's a spectrum analyzer made that has that kind of accuracy. Typically, it's more like 0.2 or 0.5 dB (5% - 12%).

Hello all of you,

Op vr 8 jul. 2022 om 19:58 schreef DP <dpoinsett@...>:

For DC or low frequency AC, the return current path in this circuit is on
the bottom copper plane directly immediately between the two ports and
diffused widely over the rest of the bottom surface. As the signal
frequency is increased, the electrical and magnetic fields begin to
concentrate almost entirely in the small space between the top trace and
the bottom copper plane. At RF frequencies, the return current path on the
bottom plane is directly below the trace and NOT between the ports even if
they are close.

Perhaps this is related: When transporting non-DC currents in a coax, both
the shield and the core need to be transporting the TE mode, and thus the
coax has to be the return path and not the connection between the port-1
and port-2 of the NanoVNA.

RF return current always flows via the path of least reactance. Here's
more info:

Nice article!

Thanks,

Victor

"On the port 0 I connect shield and center conductor (as with any coaxial transmission line), on the other port I do the same. Simple connection, nothing fancy. Shield to shield, hot to hot :)"

"Now I have internally bonded ground between shields at Port 0 and Port 1, and i ALSO have shield of the coaxial cable connecting grounds of those two ports!!! THAT DOES NOT SEEM RIGHT!"

Hi Miro,

With a properly connected and calibrated S21 setup, the internal ground connection between ports in the Nano is not a problem. There is almost no RF current along that path, and calibration will account for the very very small amount that may exist. I know this seems counter-intuitive.

Imagine a large double-sided PCB. The bottom of the board is a solid copper plane. The top has a single copper trace that starts at one edge and takes a big U-shape path across the board and returns to a nearby edge. Inject RF at the starting edge between the top trace and bottom plane (call it Port 1) and terminate the end edge with a resistor between the trace and bottom plane (call this Port 2).

For DC or low frequency AC, the return current path in this circuit is on the bottom copper plane directly immediately between the two ports and diffused widely over the rest of the bottom surface. As the signal frequency is increased, the electrical and magnetic fields begin to concentrate almost entirely in the small space between the top trace and the bottom copper plane. At RF frequencies, the return current path on the bottom plane is directly below the trace and NOT between the ports even if they are close.

It's the same in the Nano. With typical coax connections between the ports and through the device under test, there is almost no RF current in the ground connection between the Nano ports. Almost all of the RF return current flows thought the port connector, coax shield, and DUT.

RF return current always flows via the path of least reactance. Here's more info:


Dave NU8A

Standard and required practice with anything RF: BOTH ENDS of the shield
of a coaxial cable must be appropriately connected at their respective
ends / ports.

Here is my setup for measuring CMRR. Notice the "ground" is corried
through the test fixture. Also see the attachment in case this site does
not support images in the text.

[image: image.png]

Dave - W?LEV



On Fri, Jul 8, 2022 at 2:23 AM Miro, N9LR via groups.io <m_kisacanin=
[email protected]> wrote:

Some really good suggestions, but let me highlight "my problem" here :)

I'll only focus on measuring S21 in differential mode using 2 port setup!

On the port 0 I connect shield and center conductor (as with any coaxial
transmission line), on the other port I do the same. Simple connection,
nothing fancy. Shield to shield, hot to hot :)

Now I have internally bonded ground between shields at Port 0 and Port 1,
and i ALSO have shield of the coaxial cable connecting grounds of those two
ports!!! THAT DOES NOT SEEM RIGHT!

Chances are that DUT (the current balun in this case) will lessen the
impact of the internally bonded grounds by acting as the current balun, but
what if CMRR is small - parallel ground paths will add some measuring error!

I still need to take a look at the S11 concept suggested by WB2UAQ with
shorted output and 1 port measurement of S11, but that still does not give
me S21 in differential mode!

So, how will internal ground bonding affect 2 port setup for
measuring S21 in differential mode?

--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV

My favorite SDR is from AirSpy. Excellent quality and SW (free) support.

Dave - W?LEV

--
Dave - W?LEV

I use Earthlink, and they do not block it, but I think I had to add the groups to my address book to avoid the SPAM filter catching them.

73, Jim

That may be true now but with the constant advance in technology and miniaturisation it seems quite likely future developments will add a substantial range of test capabilities to miniaturised NVA's. This will not be welcomed by manufacturers of expensive single purpose devices. Basically the hardware and software requirements for spectrum analysis within these NVA's lend themselves to adding RFI analysis capabilities to these test instruments.

David Southwell ARPS EFIAP CPN(g)
Party Wall Surveyor,
Commercial Property Developer and Consultant
Photographer
________________________________
From: [email protected] <[email protected]> on behalf of W0LEV via groups.io <davearea51a@...>
Sent: Friday, July 8, 2022 16:44
To: NANO VNA <[email protected]>
Subject: Re: [nanovna-users] NanoVNA Is it possibel to add RFI capability

The NANOVNAs are not the proper instrument to use for sleuthing RFI. A
battery powered receiver in the AM band is excellent. Also, the TinySA is
a small highly affordable spectrum analyzer which is suited for the
purpose.



Dave - W?LEV

On Fri, Jul 8, 2022 at 2:46 PM David Southwell <David.Southwell@...>
wrote:

So many smmall devices and somjetimes power supplies generate RFI.
Would it be possible to add a sensor to assist in detection, identifion
and measuring RFI from such devices.
Seems a logical extension but I do not have technical skill to know how it
might be doen.
It would certainly need something to prevent the Nanovna being overwhelmed
by powerful signals.
Would be really useful to have such capability in the shack
David M0TAU

--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV

On Fri, Jul 8, 2022 at 08:47 AM, F1AMM wrote:

I say that, to follow what you are discussing, which seems interesting to me, there is a cruel lack of diagrams.

You are right :) Here is a quick diagram (see attached) that shows:
* 2 port setup
* internally bonded grounds for two nanoVNA ports
* two "available" paths the return current can take (through DUT and through internally bonded ground)