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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)

Use a VPN to connect to the Internet. While there are free VPNs, you should be able find a good deal on a lifetime plan for a premium VPN service, as these are preferable, through Groupon or StackSocial for dirt cheap.

Connecting through a VPN typically allows you to circumvent your ISP's restrictions, and in the process shroud your activity from them as well.

I think this might be better posted in the group manager's forum. A web search turned up several instances of this over the last few years.

You could also contact GIO support about it. And it never hurts to contact Earthlink. You'll have to ask for level 2 support since level 1 will go through scripts that won't likely be helpful, though you'll probably have to let them go through the scripts first before you can get to level 2.

Donald KX8K

If you can put together a small computer / display with an RTL-SDR unit,
that would work great for that purpose. My favorite USB SDR unit so far is
the FunCube dongle.

Zack W9SZ

On Fri, Jul 8, 2022 at 10:44 AM W0LEV <davearea51a@...> wrote:

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

<>
Virus-free.
www.avg.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

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

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