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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

I say that, to follow what you are discussing, which seems interesting to me, there is a cruel lack of diagrams.
F1AMM (Fran?ois)

But the smith tells you a lot about the frequency response over a given area...
On single port test i measure
Return loss...
Swr...
Phase..
And Smith
Dg9bfc sigi

Am 08.07.2022 11:56 schrieb Arie Kleingeld PA3A <pa3a@...>:

You can measure the insertion loss of a common mode choke made from coaxial cable that is air wound or wound on a ferrite core by connecting the shield end of the choke between the center conductors (hot leads) of the two connectors on the nanoVNA after doing a standard calibration of nanoVNA using the standard method.
The common grounds between the connectors will not affect the insertion loss between the center conductors of the two connectors.
The center conductor of the common mode choke does not need to be connected to anything. You are just measuring the insertion loss of the shield connections to the common mode coaxial choke.

If not interested in Smith Chart,

touch the nanoVNA's display, then choose trace, switch off the Smith trace.

73

Arie

Op 8-7-2022 om 07:39 schreef Observer:

Not interested in Smiths

Hello

nanoVNA without technicality seems unnatural to me. It is a measuring device; you must therefore master what it measures, otherwise it will not be too useful to you.

The current use of the Smith has nothing to do with the use for which it was designed and used. Before, we used the Smith, at a fixed frequency, to calculate graphically. Now we use the Smith to represent, in a frequency band, an impedance. With computers, there is no point in making calculations graphically: it is long and imprecise.

You will notice that the Smith that appears on the nanoVNA is not scaled and the graph you see is a trace because the frequency is swept.

--
F1AMM Fran?ois

-----Message d'origine-----

De la part de Observer
Envoyé : vendredi 8 juillet 2022 07:40

Maybe it's better to say what you want in stead off your non-interested. I personally use it for that, what are your intensions.

73 Alex, PE1EVX

Hello Mito,

In the differential mode how will that internal common ground affect

measurements as it will effectively short the current that is supposed to
go through the shield of the coaxial cable making the balun?

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!

I see sometimes a transformer when measuring the differential mode:
; DM Measurement
b).
I though don't think this solves your question... So you have a good
question.

All the best,

Victor


Op do 7 jul. 2022 om 22:26 schreef Miro, N9LR via groups.io <m_kisacanin=
[email protected]>:

Found several articles and several answers/opinions on this topic :)

If I want to do 2 port measurement in a setup where the input and output
of the DUT do NOT have common ground (let's say an RF transformer, or a
simple current balun), how will internal common ground on nanoVNA ports
affect measurements.

Let's be even more specific - want to do some simple testing of an HF
balun. S21 for differential mode and for the common mode suppression. Just
for the sake of the argument, balun will be wound with a short (comparing
to lambda) piece of coaxial cable, either wound in air or on ferrite toroid.

In the CMR mode I'l short both sides of the balun, connect to "hot" ends
of both nanoVNA ports, and "rely" on the grounds being connected internally
- is that correct setup?

In the differential mode how will that internal common ground affect
measurements as it will effectively short the current that is supposed to
go through the shield of the coaxial cable making the balun?

So, in one case (CMRR measurement) that internal common ground helps. but
in the other (differential) it does not.

All would be easier if ports on nanoVNA are not bonded internally and I
have an option to connect them or not :)

On 08/07/2022 06:39, Observer wrote:

Hi,
I am a newbie here and on nanoVNA
Any online sources for how to use, without too much technicality, for antenna z, resonance, lc resonance and L inductance. Not interested in Smiths

Also:
/g/nanovna-users/wiki#For-Beginners-and-Experienced-Users

David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

On 08/07/2022 06:39, Observer wrote:

Hi,
I am a newbie here and on nanoVNA
Any online sources for how to use, without too much technicality, for antenna z, resonance, lc resonance and L inductance. Not interested in Smiths

There are a three books you might like to look at:





Smith charts can be helpful to show resonance, cable lengths (e.g. 90 degree
phase shift) etc., and will likely be explained in the books I mentioned.

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Hi,
I am a newbie here and on nanoVNA
Any online sources for how to use, without too much technicality, for antenna z, resonance, lc resonance and L inductance. Not interested in Smiths

Miro, the nanovna is designed to measure this way - think of the
calibration you do for a thru S21 measurement; it calibrates the error due
to the cable and ground paths.
For measuring the choke, there is no need to worry about this issue. Other
issues are present which have a much larger effect on the
resolution/accuracy of an S21 measurement - it is quite accurate for small
values of Z, but gets less and less accurate as Z exceeds several k-ohms.
But it is entirely sufficient to get a reasonable measure of the
effectiveness of the choke, especially for the values of insertion loss and
common-mode S21 attenuation.

On Thu, Jul 7, 2022 at 7:23 PM 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?

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?

Anybody have any hints on getting Earthlink to stop blocking groups.io?

I do this a little differently, for simplicity, as discussed in some of the
message threads (search for CMC, and you will find lots of methods/info
from discussions several months ago).
For insertion loss, with a coaxial coax choke like what you described, what
I care about is the loss through the center conductor when the shield is
working as a return path - so I just hook it directly to the coax port 0
and 1 connectors of the nano, and display the S21 loss curve in dB. A good
choke will have just a small insertion loss, typically less than .1 dB at
HF frequencies.
For common-mode rejection, what I care about is how much the shield
attenuates the signal - so I connect the shield only to the center
conductors of the port 0 and 1, and do another S21 loss curve. Then I see
20-40 dB of attenuation in a curve across 1-30MHz for my HF chokes. If I
want to see the impedance, I can also change the display to show R+jX and
get an estimate of the impedance, hoping for k's of ohms resistive and a
small reactive part. The measurement and values are not perfect, but is
easy to do. You can see a similar loss curve if you just hook the shield
across port 0, and display an S11 loss curve - but displaying the impedance
isn't correct in that setup, since it is the impedance of the reflection,
not of the choke.

As you said, short the input terminals and the output terminals and measure S21 between the terminals with them floating. With the phase and magnitude of S21 the common mode Z can be calculated. There are files in this discussion group that do the calculation. Save the s2p data and insert it into the spreadsheets.
For insertion loss measure S11 (return loss format) looking into the DUT with the output terminals of the DUT shorted. Half the return loss is the loss thru the DUT.

[Siegfried said: In both cases a common ground does not hurt so i connect both grounds together]

That's what I was hoping for :)

That common/internal ground (bonding) can't affect when measuring against 50ohm load (1 port measurement), but I was concerned how will that affect S21 (through loss).

Any "science" beyond empirical finding that internal bonding won't hurt? A gut filling tells me that there much be more to it when I have two ground paths in parallel - one internal and one through DUT.

When it comes to "how much power" - that would be great for another release - nanoVNA with legal power output (1k5W) and temperature sensor built in :) + other port that can handle these levels too! And battery to support all that!

I measure through loss
And cm surpression
In both cases a common ground does not hurt so i connect both grounds together
And i measure swr
with the balun loaded with its nominal impedance.. 50 ohms.. Or 200 (for a 1 to 4).. Or for whatever it is made
Those three tests give you a good idea how well your balun or choke works
How much loss it has
How good it suppresses cm current
And in what frequency range you can use it... Whatelse do you need to know?? Maybe how much power it can handle.. Grin
Greetz sigi dg9bfc

Am 07.07.2022 22:25 schrieb "Miro, N9LR via groups.io" <m_kisacanin@...>:

Found several articles and several answers/opinions on this topic :)

If I want to do 2 port measurement in a setup where the input and output of the DUT do NOT have common ground (let's say an RF transformer, or a simple current balun), how will internal common ground on nanoVNA ports affect measurements.

Let's be even more specific - want to do some simple testing of an HF balun. S21 for differential mode and for the common mode suppression. Just for the sake of the argument, balun will be wound with a short (comparing to lambda) piece of coaxial cable, either wound in air or on ferrite toroid.

In the CMR mode I'l short both sides of the balun, connect to "hot" ends of both nanoVNA ports, and "rely" on the grounds being connected internally - is that correct setup?

In the differential mode how will that internal common ground affect measurements as it will effectively short the current that is supposed to go through the shield of the coaxial cable making the balun?

So, in one case (CMRR measurement) that internal common ground helps. but in the other (differential) it does not.

All would be easier if ports on nanoVNA are not bonded internally and I have an option to connect them or not :)

On Wed, Jul 6, 2022 at 10:26 PM, <t.rohner@...> wrote:

HB9SFG

Hello and many thanks for the infomation. Good to hear, there is a solution that fixes the problem. The 1.0.53 is also for my Nano the latest version that worked without the mentioned issue. Recently I updated to 1.2.00, which is much more stable but also with this version I faced the same issue. The problem seems to be hardware dependent.
I will look for version 1.2.02 and give it a try.

Many thanks and 73
Gerd