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Hi all
something doesn't seem to be working very well, the most recent firmware 1.2.40 of DiSlord installed on SEESII H4, I really appreciated the characteristic impedance conversion function for SWR measurements and for the Smith graph, but the impedance values ??of port2 should not change in fact they are what they are.
but by measuring the input of port2 with the S11 Smith function it gives 77.7 Ohm as long as the conversion value 50-->77.7 Ohm is configured while it is supposed to give 50 Ohm, then by putting a 50 Ohm load on S11 Smith it displays the value 50 Ohm,
So the Port2 impedance seems has really changed impedance when we put 50 Ohm --> 77.7 Ohm if not how can we explain this displayed value which does not match our 50 Ohm prediction ?
73's Nizar
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In doing so, you have reassigned the center of the Smith Chart to 77.7 ohms. Therefore, even if your are measuring a matched 50-ohm resistor, it will read 77.7-ohms. Set it to 200 ohms, and a 50-ohm resistor will read 200 ohms. Set it to 50-ohms and it will read 50-ohms. Set it to "1", unity, and you have a normalized chart that can read, after scaling properly for the normalization, anything you use. Dave - W?LEV On Wed, Jan 22, 2025 at 7:41?PM Team-SIM SIM-Mode via groups.io <sim31_team= [email protected]> wrote: Hi all
something doesn't seem to be working very well, the most recent firmware
1.2.40 of DiSlord installed on SEESII H4, I really appreciated the
characteristic impedance conversion function for SWR measurements and for
the Smith graph, but the impedance values ??of port2 should not change in
fact they are what they are.
but by measuring the input of port2 with the S11 Smith function it gives
77.7 Ohm as long as the conversion value 50-->77.7 Ohm is configured while
it is supposed to give 50 Ohm, then by putting a 50 Ohm load on S11 Smith
it displays the value 50 Ohm,
So the Port2 impedance seems has really changed impedance when we put 50
Ohm --> 77.7 Ohm if not how can we explain this displayed value which does
not match our 50 Ohm prediction ?
73's Nizar
-- *Dave - W?LEV* -- Dave - W?LEV
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On Wed, Jan 22, 2025 at 01:31 PM, W0LEV wrote:
In doing so, you have reassigned the center of the Smith Chart to 77.7
ohms. Therefore, even if your are measuring a matched 50-ohm resistor, it
will read 77.7-ohms. Set it to 200 ohms, and a 50-ohm resistor will read
200 ohms. Set it to 50-ohms and it will read 50-ohms.
This is incorrect. Changing the system impedance will NOT change the measured impedance value. It only changes metrics based on Zo like Smith Chart plot, Return Loss & SWR.
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On Wed, Jan 22, 2025 at 11:41 AM, Team-SIM SIM-Mode wrote:
something doesn't seem to be working very well, the most recent firmware
1.2.40 of DiSlord installed on SEESII H4, I really appreciated the
characteristic impedance conversion function for SWR measurements and for the
Smith graph, but the impedance values ??of port2 should not change in fact
they are what they are.
but by measuring the input of port2 with the S11 Smith function it gives 77.7
Ohm as long as the conversion value 50-->77.7 Ohm is configured while it is
supposed to give 50 Ohm, then by putting a 50 Ohm load on S11 Smith it
displays the value 50 Ohm,
The measured impedance will NOT change when you change the system impedance in the Menu. DiSlord has made some changes to the firmware since this function was introduced and I recall this made some errors. On his beta firmware group he has done an update and latest firmware has been released for beta testing. Here are some screenshots done with an older version 1.2.20 that re correctly displayed and calculated. You will note that measured impedance does not change when changing the system inmpedance. What does change is the Return Loss calculation and the Smith Chart plots. Roger
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I did not intend to change the measurement, only the displayed value. The measurement is unchanged. Dave - W?LEV On Thu, Jan 23, 2025 at 12:39?AM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Wed, Jan 22, 2025 at 01:31 PM, W0LEV wrote:
In doing so, you have reassigned the center of the Smith Chart to 77.7
ohms. Therefore, even if your are measuring a matched 50-ohm resistor, it
will read 77.7-ohms. Set it to 200 ohms, and a 50-ohm resistor will read
200 ohms. Set it to 50-ohms and it will read 50-ohms.
This is incorrect. Changing the system impedance will NOT change the
measured impedance value. It only changes metrics based on Zo like Smith
Chart plot, Return Loss & SWR.
-- *Dave - W?LEV* -- Dave - W?LEV
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On Wed, Jan 22, 2025 at 05:09 PM, W0LEV wrote:
I did not intend to change the measurement, only the displayed value. The
measurement is unchanged.
The displayed impedance remains the same regardless of the system impedance setting if the firmware does the calculation correctly. See my earlier screenshots. Roger
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The impedance of port 2 is also recalculated to the specified value. And it is assumed that S22=S11, S12 = S21
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Hi
Roger , i am agree with you , when setting 50ohm-->77.7ohm and measuring with S11 Smith function an external impédance we have always the correct impédance value displayed as expected no mater what impedance base used only smith graph or SWR or loss return can be changed , which is correct and expected , until this point all seems to be normal as expected and we are very happy with.
The strange thing occure only when trying to measure port2 with the same function without changing any think , just by hooking port2 as impedance to be measured and then we are surprised to have 77.7ohm displayed , thats means port2 hardware impedance has really changed value wich is not expected , i assume that port2 hardware is always at the same value fixed by hardware implementation to 50ohm as shown in hardware drawing and not fixed by firmware !!! Did i misunderstand some thing ?
Thanks
73s Nizar
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Hi Dislord
Thanks for response, but wondering why S11 impeadance measurement seems to include also port2 input measurement what can explaine this strange displayed impedance of port2 , i assume that S11 measurement should include only port1 measurement no matter what we have on port2 hardware, example an external frequency generator hooked there ... .
Not sure but i guess may be calibration calculation may mixe port1 and some portion port2 measurement , i dont know ??
73s Nizar
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Port-Z is analogue of this
(z)-c.html
Or search
Impedance Renormalization
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I’m confused - does firmware version 1.2.40 display this properly or was this corrected in the new beta version Roger mentioned? Tony On Thu, Jan 23, 2025 at 1:08?AM DiSlord via groups.io <dislordlive= [email protected]> wrote: Port-Z is analogue of this
(z)-c.html
Or search
Impedance Renormalization
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On Wed, Jan 22, 2025 at 11:41 AM, Team-SIM SIM-Mode wrote:
Hi all
something doesn't seem to be working very well, the most recent firmware
1.2.40 of DiSlord installed on SEESII H4, I really appreciated the
characteristic impedance conversion function for SWR measurements and for the
Smith graph, but the impedance values ??of port2 should not change in fact
they are what they are.
but by measuring the input of port2 with the S11 Smith function it gives 77.7
Ohm as long as the conversion value 50-->77.7 Ohm is configured while it is
supposed to give 50 Ohm, then by putting a 50 Ohm load on S11 Smith it
displays the value 50 Ohm,
So the Port2 impedance seems has really changed impedance when we put 50 Ohm
--> 77.7 Ohm if not how can we explain this displayed value which does not
match our 50 Ohm prediction ?
Nizar, In my other post I mentioned that the NanoVNA measures the actual impedance and gave several screenshots that were S11 shunt measurements. These were made using only CH0 and a test jig. Ch1 was not used for these tests. I pointed out that even when you change reference impedance the impedance measurement is the same for S11 shunt measurements . What I neglected to do was post what happens when you do measurements of CH1 when you change the reference impedance. This was an error on my part and I apologize to the group if this caused confusion and disagreement. I made a complete set of measurements using CH0 alone in S11 shunt mode and some S11/S21 measurements. I have put them in a pdf report because this group does not permit inline text and photos. It is attached to this post. You will note that your measurements were correct but the reason why needs to be explained. When you change the reference impedance from 50 ohms the hardware will still make measurements in the same way but the firmware will adjust all the calculations to be based on the new reference impedance. This includes the measurement of CH1 if you are connected directly to it. So if you selected 75 ohms as the reference impedance the measurement of CH1 will be close to 75 ohms even though it is physically closer to 50 ohms. In the attached report I show an example where I put 200 ohms in series between CH0 and CH0 and the measurement on the Smith Chart is 275 ohms (200+75). Regards - Roger
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On Thu, Jan 23, 2025 at 09:42 AM, Tony Scaminaci wrote:
I’m confused - does firmware version 1.2.40 display this properly or was
this corrected in the new beta version Roger mentioned?
I downloaded and used 1.2.40 today with the reference impedance change feature (Port Z under display). It works OK. The newer beta version (not publicly released) fixes some other issues. DiSlord is always doing improvements, code refactoring and small bug fixes to make it better. We owe him a lot for all the work he does. Roger Roger
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Hi
Thank you Roger for all your explanation,
So the 1.2.40 finally is doing the correct job as its wanted to do, but not what i expected, so i just need to consider that reference impedance change to 75ohm for exemple , need to include some portion of S12 physical measurement to correct the S11 smith measurement as we assume that we have a virtual impedance of 75 ohm on port2, so i just need to know it as its designed by DiSlord, .
Conclusion : physically port2 should be free and clean even if we use only S11 with just port1 connection , because port2 measurement is also used during reference impedance change to ensure its virtual 75ohm imput instead of 50ohm physically impedance , so a 50 ohm load hooked on port2 is highly recommended even when measuring only S11 with just port1 .
So what i measured in port2 with S11 smith is the supposed virtual 75 ohm and not what i expected to measure 50 Ohm physical impedance.
Thanks to Dislord for this pertinent firmware developpements and improvements .
73s Nizar
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Thanks for the clarification Roger. My H4 is still on the older firmware it shipped with so I’m reading through these messages to decide if and when I should upgrade. DiSlord has done a great job and his efforts are greatly appreciated. Tony On Thu, Jan 23, 2025 at 6:26?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Thu, Jan 23, 2025 at 09:42 AM, Tony Scaminaci wrote:
I’m confused - does firmware version 1.2.40 display this properly or was
this corrected in the new beta version Roger mentioned?
I downloaded and used 1.2.40 today with the reference impedance change
feature (Port Z under display). It works OK. The newer beta version (not
publicly released) fixes some other issues. DiSlord is always doing
improvements, code refactoring and small bug fixes to make it better. We
owe him a lot for all the work he does.
Roger
Roger
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On Fri, Jan 24, 2025 at 10:01 AM, Tony Scaminaci wrote:
Thanks for the clarification Roger. My H4 is still on the older firmware it
shipped with so I’m reading through these messages to decide if and when I
should upgrade. DiSlord has done a great job and his efforts are greatly
appreciated.
I updated from 1.2.20 to 1.2.40 and was pleasantly surprised. The "Enhanced Mode" for S21 and the ability to measure your 50 ohm load and then enter the load resistance increases the accuracy which is especially useful for impedance measurements.
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Hi
Roger , we can measure the real coaxial caracteristic impedance by DiSlord coax function with more accuracy then the commercial announced value for our specific portion of cable to be used example 77.7 Ohm instead of announced 75.0 Ohm , and then enter this value on the 50 --> Zc=77.7 reference change then we can mesure SWR , return loss .. ect on this portion of cable with more accuracy .
but please can you clarify us more how you can measure impedances with more accuracy with your new method ? it's a little bit confused for me . an example with screenshoots can help a lot, Thanks .
73's Nizar
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The ability to enter the value of the load resistance is only used to increase the accuracy of calibration. Small deviations from 50 ohms can then be compensated for. The cal load supplied with my NanoVNA measured 50.86 ohms at DC so I used that as my entry.
I find this feature gives me more accurate impedance measurements but it does not significantly affect SWR.
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Again, remember, we are "amateurs". We do not run a metrology lab (well, maybe one or two of us might?). 50.86-ohms DC resistance is plenty good enough. And consider the accuracy of the DMM with which you measured that 50-ohm calibration source at 50.86-ohms. For example, I have three DMMs handy on my electronic workbench. I measured one of my HP 909C type-N calibration standards with each of those three DMMs. Here are the results: 1) 50.279 Ohms (an HP benchtop DMM) 2) 50.1 Ohms (an older Sperry DMM) 3) 50.2 Ohms (a "cheap" Harbor Freight DMM) The number of significant digits directly reflects what is displayed by each of the DMMs. Which is correct? I SERIOUSLY doubt the differences would be of ANY significance in amateur radio work! Dave - W?LEV On Sat, Jan 25, 2025 at 4:59?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: The ability to enter the value of the load resistance is only used to
increase the accuracy of calibration. Small deviations from 50 ohms can
then be compensated for. The cal load supplied with my NanoVNA measured
50.86 ohms at DC so I used that as my entry.
I find this feature gives me more accurate impedance measurements but it
does not significantly affect SWR.
-- *Dave - W?LEV* -- Dave - W?LEV
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On Sat, Jan 25, 2025 at 09:30 AM, W0LEV wrote:
Again, remember, we are "amateurs". We do not run a metrology lab (well,
maybe one or two of us might?). 50.86-ohms DC resistance is plenty good
enough.
The number of significant digits directly reflects what is displayed by
each of the DMMs. Which is correct? I SERIOUSLY doubt the differences
would be of ANY significance in amateur radio work!
Dave, You are making a blanket statement when you say we are all "amateurs" here or talk about "amateur radio" work. This is NOT an amateur radio group. There are many of us in the group that are professional RF engineers or technicians and we strive to get the best performance possible out of the NanoVNA. If it were not for people like DiSlord (firmware), Zareth and Rune ( NanoVNA Saver) and OneofEleven, Owen Duffy and DiSlord (NanoVNA app) striving to squeeze the best accuracy and features from the NanoVNA we would not have the exceptional device we are using today. And some of us do own test equipment that can measure resistance to several decimal places with digits that are significant. So if you don't wish to achieve the best accuracy possible with the device that is your choice but please enough with these "we do not run a metrology lab" comments that you make from time to time. It is discouraging and dismissive to those of us trying to show how the NanoVNA can be used to its full potential. Roger Need
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Roger Need
