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On Sun, Jul 10, 2022 at 08:09 PM, Jerry Stuckle wrote:

Actually, that's a common, but incorrect statement. Current - RF or otherwise
- always flows along ALL available paths, split according to the inverse of
the resistance.
//
Jerry, AI0K

Hi Jerry,

You're absolutely right. It's not all or nothing. A semantically better way to say it is: RF current always favors the path of least impedance. The degree of "favor" is divided between paths according to impedance. That's consistent with your point.

In the case of Miro's original question about problems with RF current flowing in the internal ground connection between the ports, the answer is still no. The impedance in PATH1 of his drawing (attached) is too high for there to be a problem even though the DC resistance is probably very low. The RF return current is confined almost entirely in the transmission line.

The attached drawing shows a double-sided PCB. The bottom has a solid copper ground plane. The top has a single trace between the ports. An RF input signal is applied between the trace and ground plane. The load is connected between the trace and ground plane.

At 10 MHz the RF return current will be confined to a narrow path in the ground plane directly below the top trace. Openings in the PCB provide isolated current paths A and B for easy measurement. RF current in these paths will be negligible.

At RF frequencies, the impedance through paths A and B is high primarily due to the geometry. The further the distance from the trace, the higher the series inductance and the lower the parallel capacitance. These both mean higher reactance. The area in the ground plane directly below the trace has the lowest impedance. That's where almost all the return current flows even though it's surrounded by an area with very low DC resistance.

Like so many things with RF, this behavior is counter-intuitive to our understanding of what happens with DC and low-frequency AC.

Dave NU8A

The measure of a "good" antenna is how well it performs. When I lived in a
house with a lot bigger yard a few years ago I had a 40 meter vertical
full-wave loop antenna (~12 feet high and ~58 feet long). It had 5.5 dB of
gain over a dipole according to NEC2. It performed almost as well as a 40
meter Yagi antenna in its peak directions. It was the best 40 meter antenna
I have owned. I now live on a much smaller property and can't fit that
antenna in the yard. I have an MFJ 1796 vertical. It does "OK" on 20 meters
and higher, but I'm severely disappointed in its performance on 40 meters.
Maybe the other antenna spoiled me.

Zack W9SZ

On Mon, Jul 11, 2022 at 12:14 PM W0LEV <davearea51a@...> wrote:

Yes, indeed...... The measure of a "good" antenna is not SWR.

Of course, a 1:1 in a 50-ohm non-reactive system is essential to keep the
transmitter output stage happy, but does not measure how good an antenna is
at radiating the RF energy fed to it. Again,......SWR is NOT a single
proper indicator of a "good" antenna.

Dave - W?LEV

On Mon, Jul 11, 2022 at 6:34 AM olivier LAVAUX <f6cng.68@...> wrote:

be careful not to have a dummy load @swr1.1!
what is important is the radiated power! so not only check SWR but also
radiated electromagnetic field!
73

F6CNG Olivier



Le mer. 6 juil. 2022 à 10:24, olivier LAVAUX via groups.io <f6cng.68=
[email protected]> a écrit :

Fitst check continuity before all with and without short circuit on the
antenna itself!

73 Olivier F6CNG

Le dim. 3 juil. 2022 à 09:21, Lucian <lucian@...> a écrit :

Thanks, but you were too quick to dismiss the human factor..

It wasn't until this morning that I realised the antenna is rp-sma

female

and the nanovna is sma female.. They will screw in perfectly, yet no

core

contact... facepalm.

I'll need to buy some adapters.

Have a nice day!

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


--
Dave - W?LEV

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

You're correct. I was thinking about it and tried it: the NanoVNA does go to 900 MHZ. And all this time I thought that since the default stop freq that it 'boots up with' is 250 Mhz that it was not capable of going higher. That will teach me to test before opening my mouth.

This makes me feel better: less worried 'bout changing firmware.
Mark Walter

Hello Ed,

I have not much now to look into this, but this article:

Gives your method (Fig 3b and Fig 7a.
So one can measure some aspects of the choke.

I need to check how close this is to the DM mode.

All the best,

Victor

Op ma 11 jul. 2022 om 08:20 schreef Ed G8FAX <ed@...>:

it should go to 900 (3rd harmonic) or 1.5 g (fith overtone)

dg9bfc sigi

(sorry i can not help with fw cause i am a v2 user that has a clock to over 4g)

Am 11.07.2022 um 18:44 schrieb m2walter@...:

Yes, indeed...... The measure of a "good" antenna is not SWR.

Of course, a 1:1 in a 50-ohm non-reactive system is essential to keep the
transmitter output stage happy, but does not measure how good an antenna is
at radiating the RF energy fed to it. Again,......SWR is NOT a single
proper indicator of a "good" antenna.

Dave - W?LEV

--
Dave - W?LEV

I have an original NanoVNA: it only goes up to 250 MHz. Can I upgrade the firmware and obtain additional functionality? If the firmware can be upgraded which version should I load. Tks.
Mark Walter

Thanks.

I build a deb package with the command "DEB_BUILD_OPTIONS=nocheck python setup.py --command-packages=stdeb.command bdist_deb". You need the debian package "python3-stdeb" (Python to Debian source package conversion plugins for distutils) and maybe some more development packages.
As a quick start see this documentation:

Yes, you are right, but how do you check radiated electromagnetic field !

Tell us how you do
73
--
F1AMM Fran?ois

be careful not to have a dummy load @swr1.1!
what is important is the radiated power! so not only check SWR but also
radiated electromagnetic field!
73

F6CNG Olivier



Le mer. 6 juil. 2022 à 10:24, olivier LAVAUX via groups.io <f6cng.68=
[email protected]> a écrit :

Fitst check continuity before all with and without short circuit on the
antenna itself!

73 Olivier F6CNG

Le dim. 3 juil. 2022 à 09:21, Lucian <lucian@...> a écrit :

Thanks, but you were too quick to dismiss the human factor..

It wasn't until this morning that I realised the antenna is rp-sma female
and the nanovna is sma female.. They will screw in perfectly, yet no core
contact... facepalm.

I'll need to buy some adapters.

Have a nice day!

Hi Victor,

Thanks for your feedback, you ask a good question concerning its validity.

I’m not aware of any specific articles on the technique I mentioned, I derived that configuration from a simple circuit analysis of the differential mode wiring of a CMC = a series connected circuit with voltage drop measured across a load resistor.

I’d be interested to hear what concerns you have with my test arrangement.

Kind regards

Ed, G8FAX

Jerry, Precisely correct, Interestingly, when I first heard that: "always takes the path of least resistance"?statement it was within the context of the propensity of a lightning strike. The tallest, or best grounded?item within range (path of least resistance) typically having a greater chance of being struck during a?lightning storm. However, with regard to normal electrical flow, and function you are 100% correct,?and make a very important point. Current?always flows along ALL available paths, split according?to the?inverse of?the resistance.

Actually, that's a common, but incorrect statement. Current - RF or otherwise - always flows along ALL available paths, split according to the inverse of the resistance.

To make it simple, let's say there are two paths. One has 10 ohms resistance and one has 5 ohms resistance. If you apply 10V to the circuit, 1amp will flow though the first path and 2 amps though the second path.

The same goes for milliohm paths like those found in grounds.

Jerry, AI0K

Tnx Dave!

Nice and short write-up of what's happening.

73

Arie PA3A

Op 8-7-2022 om 19:57 schreef DP:

I put here my log of the installation on Windows but this log is in French. I can send it to you in Word if you want to translate it.



At home 2 drivers coexist, each creating a different com port from the USB interface. The log shows that only when Windows detects a device on the USB port loads the correct driver. It is impossible to preload the miscellaneous. Obviously this diver must be present on the disk for Windows to look for it.
--
F1AMM Fran?ois

Are you certain that you have the correct port selected for the NanoVNA? And are you certain that the software on the NanoVNA is reasonably current?

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

In about 75 seconds the NanoVNA Saver main screen finally shows up. But when I try to connect to the VNA comm port it quickly times out:
NanoVNASaver.Hardware.NanoVNA_2 - ERROR - Timeout reading version registers. Got: b' '
NanoVNASaver.Controls.SerialControl - ERROR - Unable to connect to VNA: Timeout reading version registers
<more debug stuff if you want it>
This is on a freshly booted NUC i5 2.2GHz 16GB RAM 64 bit Win 10 Pro
VNA-qt runs so the VNA, USB cable, etc are OK.

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