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Re: Perfect SWR with dummy load, but huge with antenna

F1AMM
 

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

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

-----Message d'origine-----
De la part de F6CNG
lundi 11 juillet 2022 08:35


Re: Perfect SWR with dummy load, but huge with antenna

 

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 ¨¤ 10:24, olivier LAVAUX via groups.io <f6cng.68=
[email protected]> a ¨¦crit :

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

73 Olivier F6CNG

Le dim. 3 juil. 2022 ¨¤ 09:21, Lucian <lucian@...> a ¨¦crit :

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!










Re: Common ground and 2-port measuring

 

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


Re: Common ground and 2-port measuring

 

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.

On Sunday, July 10, 2022 at 08:09:48 PM EDT, Jerry Stuckle <jerry@...> 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.

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


Re: Common ground and 2-port measuring

 

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


Re: Common ground and 2-port measuring

 

Tnx Dave!

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

73

Arie PA3A

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

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


Dave NU8A


Re: Fake NanoVNA? Or short between the headset :)

F1AMM
 

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

-----Message d'origine-----
De la part de Tim Dawson
Envoy¨¦ : samedi 9 juillet 2022 21:54


Re: Fake NanoVNA? Or short between the headset :)

 

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?

On July 9, 2022 1:34:23 PM CDT, Douglas Butler <sherpadoug@...> wrote:
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.




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


Re: Fake NanoVNA? Or short between the headset :)

 

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.


Re: Fake NanoVNA? Or short between the headset :)

 

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


Re: Fake NanoVNA? Or short between the headset :)

 

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


Re: Fake NanoVNA? Or short between the headset :)

 

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

On 09/07/2022 16:12, Douglas Butler wrote:
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?




Re: Fake NanoVNA? Or short between the headset :)

 

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?


Re: Fake NanoVNA? Or short between the headset :)

F1AMM
 

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


Re: Fake NanoVNA? Or short between the headset :)

 

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


Re: Common ground and 2-port measuring

 

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


Re: Fake NanoVNA? Or short between the headset :)

 

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

On Fri, Jul 8, 2022 at 10:07 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.

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





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


Fake NanoVNA? Or short between the headset :)

 

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.


Re: Common ground and 2-port measuring

 

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


Re: Common ground and 2-port measuring

 

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