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There are quite a number of cheap and useful signal generators offered on
epay.

Dave - W?LEV

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On Sat, Feb 8, 2025 at 7:03?PM Gabriele I4JXE via groups.io <gbergami=
[email protected]> wrote:

HI Philip
tnx for the advice. I use a combo of SMA M/F attenuators to stay well under
+10dBm max signal level for NanoVNA input.
Wonder if you too use FY 6XXX generator.
Gabriele, I4JXE



Il Sab 8 Feb 2025, 11:37 Philip Stevens via groups.io <philg3ses=
[email protected]> ha scritto:

Hi Gabriele,

Be careful with the level output of the FY6900 as it defaults to 5v. This
is well
above what is needed and can damage sensitive instruments such as a

tinySA

and nanoVNA port 2.

Phil g3ses

On Fri, 7 Feb 2025 at 21:12, Donald S Brant Jr via groups.io <dsbrantjr=
[email protected]> wrote:

No need, the VNA generates its own test signals internally.
73, Don N2VGU

--

*Dave - W?LEV*


--
Dave - W?LEV

HI Philip
tnx for the advice. I use a combo of SMA M/F attenuators to stay well under
+10dBm max signal level for NanoVNA input.
Wonder if you too use FY 6XXX generator.
Gabriele, I4JXE



Il Sab 8 Feb 2025, 11:37 Philip Stevens via groups.io <philg3ses=
[email protected]> ha scritto:

Hi Gabriele,

Be careful with the level output of the FY6900 as it defaults to 5v. This
is well
above what is needed and can damage sensitive instruments such as a tinySA
and nanoVNA port 2.

Phil g3ses

On Fri, 7 Feb 2025 at 21:12, Donald S Brant Jr via groups.io <dsbrantjr=
[email protected]> wrote:

No need, the VNA generates its own test signals internally.
73, Don N2VGU

Hi Roger

If the coding does not require a huge complication nor a large resources, it would be appreciated to have this option of the Z port2, it would also approach the enhanced response on H4 NanoVNA.

73's Nizar

On Sat, Feb 8, 2025 at 05:49 AM, CLIFTON HEAD wrote:

Question top left S11 SWR 250m/ 1.891 can you explain what these numbers are,
and how did you get the 250m loaded into the nanovna. Newie still leaning to
use my nano
Thanks`

The 250m is a scaling parameter on the grid . So each successive horizontal line for SWR, in this case, increases by .25. 1.891 is the SWR calculated at the marker.

Go into the Display/Scale menu to set the value you want. Click Show Grid Values to put the text on the right hand side of the screen. Later versions of DiSlord firmware have improved scaling options.

Roger

On Sat, Feb 8, 2025 at 09:15 AM, DiSlord wrote:

NanoVNA has a port renormalization function (called Port Z, see DISPLAY->PORT
Z: 50) that allows you to see the measured S parameters at other port
impedances.

But since NanoVNA is only available for measuring S11 and S21 parameters, the
following assumptions are made for renormalization: S22 = S11 and S12 = S21,
i.e. the DUT is symmetrical.
To simplify the calculations, a non-complex impedance value is used and the
new impedance of both ports is the same.

And now the question is to what extent it is necessary to make calculations
for different values ??of port impedance, because then the DUT is not
symmetrical?? and the assumption that the S22 = S11 and S12 = S21 are equal is
not true.
Or this can be useful?

DiSlord,

I have tested your port renormalization function (called Port Z) for several values of Z like 75 and 100 ohms. It calculated S11 and S21 correctly for DUT's with the same input and output impedance. I personally don't see the need to have different Z for the input and output of a DUT. I think it just makes things more complicated and very, very few users would ever use this feature.

Roger

Hi DiSlord and All

I already used the standard load= 50.83 Ohm ( DC measur by a good Multimeter's) instead of 50.00 Ohm for the Nano calibration, and a Z0= 78.9 Ohm to optimise my nominal 75 Ohm coax for the SWR and graphic smith and all seems working smoothly as it's expected for S11, measurements , but still no deep try's for S21 except Thru tests with my H4+1.2.40.
Very satisfayed right now with some precautions, very handy options and allow very accurates measurements. it's a great options , indeed an accurate professional 50 Ohm Load is expensive .
Thanks .
73's Nizar

VNA calibrated by 50Om - nominal port impedance
On measure S parameters possible calculate get Z parameters (by known Z0 = 50)

Next possible calculate from this Z new S` parameters but use Z` != 50 Om
This process named as renormalization and allow see now DUT work on other system impedances
This work on all S11 and S21 - so possible see how work filter on non 50 Om systems, or see SWR for 75Om and so on

Yes, but I believe anyone (well........."maybe") can multiply any number by
unity: 1. Or maybe not???????

Even with a normalized chart center, the measurement system is still as
close to 50 ± j 0 as Eric can economically implement.

Dave - W?LEV

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

On Sat, Feb 8, 2025 at 5:33?PM Matthew Rapaport via groups.io <quineatal=
[email protected]> wrote:

Isn't that what the Z function does--allow normalisation of the chart to
any resistance?

--

*Dave - W?LEV*


--
Dave - W?LEV

Isn't that what the Z function does--allow normalisation of the chart to any resistance?

Why not just use a normalized Smith Chart? Ten the center resistance can
be anything you want.

Dave - W?LEV

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

On Sat, Feb 8, 2025 at 5:15?PM DiSlord via groups.io <dislordlive=
[email protected]> wrote:

NanoVNA has a port renormalization function (called Port Z, see
DISPLAY->PORT Z: 50) that allows you to see the measured S parameters at
other port impedances.

But since NanoVNA is only available for measuring S11 and S21 parameters,
the following assumptions are made for renormalization: S22 = S11 and S12 =
S21, i.e. the DUT is symmetrical.
To simplify the calculations, a non-complex impedance value is used and
the new impedance of both ports is the same.

And now the question is to what extent it is necessary to make
calculations for different values ??of port impedance, because then the DUT
is not symmetrical?? and the assumption that the S22 = S11 and S12 = S21
are equal is not true.
Or this can be useful?

--

*Dave - W?LEV*


--
Dave - W?LEV

Since I use the nanoVNA only for amateur radio or tinySA related work, everything is nominally 50 Ohms. But for purely theoretical reasons I'm looking forward to any expansion on this subject you care to make. Always like learning more, even when it doesn't directly apply to what I do with these instruments. Thank you!

NanoVNA has a port renormalization function (called Port Z, see DISPLAY->PORT Z: 50) that allows you to see the measured S parameters at other port impedances.

But since NanoVNA is only available for measuring S11 and S21 parameters, the following assumptions are made for renormalization: S22 = S11 and S12 = S21, i.e. the DUT is symmetrical.
To simplify the calculations, a non-complex impedance value is used and the new impedance of both ports is the same.

And now the question is to what extent it is necessary to make calculations for different values ??of port impedance, because then the DUT is not symmetrical?? and the assumption that the S22 = S11 and S12 = S21 are equal is not true.
Or this can be useful?

Question top left S11 SWR 250m/ 1.891 can you explain what these numbers are, and how did you get the 250m loaded into the nanovna. Newie still leaning to use my nano
Thanks`
________________________________
From: [email protected] <[email protected]> on behalf of Roger Need via groups.io <sailtamarack@...>
Sent: Thursday, February 6, 2025 7:08 PM
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] SWR Question

On Thu, Feb 6, 2025 at 03:46 PM, jeffinwa wrote:

In the shop, connecting this device directly to the SO239 connector, the sweep
on the screen is perfect. But in testing with the antenna installed with coax,
and testing at the end of the feed line, the sweep seems strange.

The ripples you are seeing are not unusual. It is not due to the antenna - it is the transmission line and/or adapters being used. . When the impedance of the transmission line is slightly different than the 50 ohm impedance of the NanoVNA you get ripples which give a higher SWR at odd multiples of 1/4 wavelength (1/4, 3/4. 5/4 etc.) and lower at multiples of half wavelength (1/2, 1, 3/2 etc).

Attached are two screenshots. 50 feet of RG213 with 50 ohms at the end was measured. SWR should be close to 1. In one plot a SMA to SO239 adapter was used and in the second a SMA to PL259 adapter with a barrel connector. Those female barrel connectors have about 35 ohms of characteristic impedance. Notice how much more ripple there is with the barrel inline.

Hello Roger,

OK, understand now.
And I had checked that the scaling was the same in both tests. Not that I expected they would be different:-)
Thanks for clarifying.

Regards...Bob VK2ZRE

Hi Gabriele,

Be careful with the level output of the FY6900 as it defaults to 5v. This
is well
above what is needed and can damage sensitive instruments such as a tinySA
and nanoVNA port 2.

Phil g3ses

On Fri, 7 Feb 2025 at 21:12, Donald S Brant Jr via groups.io <dsbrantjr=
[email protected]> wrote:

No need, the VNA generates its own test signals internally.
73, Don N2VGU

No need, the VNA generates its own test signals internally.
73, Don N2VGU

On Fri, Feb 7, 2025 at 02:19 PM, <pastor.healer@...> wrote:

But to be able to see this on a screen with these vna's, amazing.

Try hooking it to the input of a manual antenna tuner with a termination on the other port, display a Smith Chart, and manipulate the tuner controls, it is quite an eye-opener.
Then remove the termination and see if you can find a match; a poor/lossy tuner will tune into its own losses and dissipate all of the transmitted power internally, another eye-opener!
73, Don N2VGU

On Fri, Feb 7, 2025 at 02:07 PM, Roger Need wrote:

How good are those SMA to PL259 and SMA to SO239 connectors that are popular
with some NanoVNA users?

Above HF/VHF anything with a "UHF" connector involved is going to exhibit increasingly poor performance. In addition nobody that I know of makes a good-quality UHF calibration kit so you will have to use adapters which degrade the calibration.
I have purged all of them from my station in favor of type N, which is good beyond 12GHz, high quality ones beyond 18GHz. I use N, BNC, SMA, and reserve type F for RX-only use.
73, Don N2VGU

One other thing that might be taken into consideration is calibration of the NanoVNA. Are you testing the antenna, or the antenna system?

When I want to test a new home made antenna, I calibrate the NanoVNA with an open, short, and 50 ohm load (assuming 50 ohm coax) to the antenna end of the coax. This allows measuring the antenna and not the coax.

Hi Folks,

A few last comments and then I'm moving on. Today I modeled (approximately) Jeffs antenna using 4NEC2 and I made a few assumptions based on Jeffs installation. I built my antenna last night and wound up with my radials bent downward at an approximate 30 degrees angle which provided a very good match at resonance and therefore I used 30 degrees bent downward radials in my model. I also guesstimated Jeffs antenna is about 2 feet from the nearby tall mast that I estimated to be approximately 8 feet tall and I left all other variables out of the picture.

Bottom line using the results of the 4NEC2 model is that the presence of the nearby mast hardly influences the feedpoint impedance at resonance (just a couple of ohms) and therefore the SWR is hardly impacted by the nearby mast but the presence of the nearby mast does cause some scalloping of the antennas radiation pattern when looking at the horizontal plane (azimuth) with peaks and valleys in the azimuth being around +/- 2.5 dB of where the azimuth pattern would be if mounted in the clear (in the clear the azimuth pattern is a pure circle even when just using 3 radials). Also note the presence of the nearby mast did not introduce minor dips in the SWR plot, the SWR plot was very smooth. Therefore the 4NEC2 model supports the theory and actual observations that the minor SWR dips (valleys) that Jeff sees when using coax and the NanoVNA to measure his antenna are not a result of the antenna or nearby mast but rather the feedline and associated connectors as we (especially Roger and I) have discussed above.

Just FYI and 73,
Don (wd8dsb)