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Re: Inductor model
On Mon, Jun 26, 2023 at 05:25 PM, Roger Need wrote:
I suggest you calibrate right at the screw terminations on the green blockRoger I compared both methods of calibration, which I refer to as "screws" and "crocs". At around 72kHz, where the reactance is approximately 50R, both calibration methods give an inductance of 108uH. However, the SRF was 7.4MHz for "screws" and 12.9MHz for "crocs". I then repeated the measurement with a different VNA, an FA-VA5. This gave L=110.7uH for "screws" and 110.5uH for "crocs". The SRF was 6.38MHz for "screws" and 6.45MHz for "crocs". I can accept the difference in L between the two devices but can't decide which one is giving me the most accurate SRF. -- Mike |
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Re: nanovna-saver crashes with H4
That is a very old version of NanoVNA Saver, download the latest
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version and try again. On Mon, 26 Jun 2023 at 23:07, Fred Moore <n40cla@...> wrote:
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Re: Inductor model
Could you post your .s1p file in shunt on port 0. I would like to reger something.
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Have you noticed that when you connect a coil or a trap (finally a dipole) by a single leg on port 0 (the other leg in the air), looking at the ROS, you can see the resonance very well. Ok, it only gives elements at the resonance frequency... but still it's very practical 73 -- F1AMM Fran?ois -----Message d'origine-----De la part de Mike Envoy¨¦ : lundi 26 juin 2023 10:23 |
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Re: Outliers in group delay measurement
Here it is, thanks for taking a minute to look into it.Attachments : - your smoothed file - the processing log (.CSV) showing the anomalies detected. - the S21 Group Delay (ns) on the smoothed file 73 -- F1AMM Fran?ois De la part de astech119 Envoy¨¦ : lundi 26 juin 2023 20:24 230621-60in01-1MHz-701MHz-1212pts-NVNA1X.s2p
230621-60in01-1MHz-701MHz-1212pts-NVNA1X.s2p
SmoothVNA.log.csv
SmoothVNA.log.csv
230621-60in01-1MHz-701MHz-1212pts-NVNA1X.png
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Re: S11 ? if Zc complexe
That's it, we have converged. In my application where I am looking for an equality between a value obtained by scanning and a target value, the distance between between the two points (in the complex plane) is a much better criterion for a good result than the ROS which only complicates by creating a non-monotonic function.
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When the result of the calculation is equal to the target, the ROS is indeed ONE and the distance zero. It is in the search for the optimal that the ROS disrupts everything. -- F1AMM Fran?ois -----Message d'origine-----De la part de Maynard Wright, P. E., W6PAP Envoy¨¦ : mardi 27 juin 2023 00:56 |
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Re: nanovna-saver crashes with H4
Thanks for the info. I do NOT use usc-c to usb-c cables. I use the
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standard original usb-a to usb-c. Can you provide a link for the latest DiSLord code? Thanks Fred On Mon, Jun 26, 2023 at 7:57?PM Stan Dye <standye@...> wrote:
I had a similar problem when I had a bad cable or a bad port connection. |
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Re: nanovna-saver crashes with H4
I had a similar problem when I had a bad cable or a bad port connection.
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Try a different cable, or a different port on the computer. Don't use a usb-c to usb-c cable, use a usb-a port on your computer. The DiSlord 1.0.64 firmware is a bit old, but is a known good version with no bugs that I know of. More recent firmware has more features, but shouldn't affect basic operations. On Mon, Jun 26, 2023 at 3:42?PM Fred Moore <n40cla@...> wrote:
I forgot to mention that the nano 2.8 hardware is on some old software. My |
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Re: S11 ? if Zc complexe
R. A. Chipman, in "Schaum's Outline Series - Theory and Problems of Transmission Lines," McGraw-Hill, 1968, points out that when a lossy transmission line has Zo complex, minimum reflection from the load will occur when Zt equals Zo but maximum power transfer will occur when Zt is the complex conjugate of Zo. This seems nonituitive, but Chipman explains that the voltage and current relationships in the two or three eighth wavelengths adjacent to the load cause the loss of power to be reduced by exactly the amount necessary to provide the extra power required in the load (page 139).
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Chipman also shows that when Zo is complex, it is possible for the reflection coefficient to be greater than 1. He shows that the maximum value for the reflection coefficient is 1 + sqrt(2) (page 137) and states on page 138: "The conclusion is somewhat surprising, though inescapable, that a transmission line can be terminated with a reflection coefficient who magnitude is as great as 2.41 without there being any implication that the power level of the reflected wave is greater than that of the incident wave." In radio work, we often assume that a lossy line has a real characteristic impedance and this is a useful approximation in most cases. Chipman points out that the relationships among the primary constants make that relationship mathematically impossible except for a line (impractical physically) for which the loss due to R equals the loss due to G. 73, Maynard W6PAP On 6/26/23 07:58, Jim Lux wrote:
On 6/26/23 7:26 AM, Fran?ois wrote:I knew about the phone lines. My problem is that if we calculate the S11 with complex values, it leads, for example, to a ROS which can be negative. S11 is no longer in a circle of radius 1.It's possible, that with some active systems, you could get a reflection that is bigger than the incident wave (i.e. if the Zload were negative). ?But I think that for an entirely passive load, the reflected wave cannot be greater than the incident wave. |
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Re: nanovna-saver crashes with H4
I forgot to mention that the nano 2.8 hardware is on some old software. My
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H4 software is also old 1.0.64. It was installed May 31 2021 Fred On Mon, Jun 26, 2023 at 5:19?PM Tim Dawson <tadawson@...> wrote:
What code version(s) are on the NanoVNA's? |
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Re: nanovna-saver crashes with H4
My Nano H4 is on a DiSlord version 1.0.64
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On Mon, Jun 26, 2023 at 5:19?PM Tim Dawson <tadawson@...> wrote:
What code version(s) are on the NanoVNA's? |
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Re: Inductor model
On Mon, Jun 26, 2023 at 05:25 PM, Roger Need wrote:
Calibrating with the crocodile clips will not give you a good reference plane.Thanks Roger, I will try that tomorrow. -- Mike |
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Re: nanovna-saver crashes with H4
What code version(s) are on the NanoVNA's?
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On Mon, June 26, 2023 5:06 pm, Fred Moore wrote:
I am confused. A friend of mine and I are trying to figure out why *my --
Tim Dawson (tadawson@...) Owner/Engineer TPC Services Bellnet: (906)-482-5732 Houghton, MI 49931 "The world is complex. Sendmail.cf reflects this...." |
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Re: nanovna-saver crashes with H4
I am confused. A friend of mine and I are trying to figure out why *my
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nano H4 and his very early nano vna with the 2.8" screen will both run on his nano saver 0.3.7.* His 2.8 nano runs on my computer on saver 0.3.8 but mine does not. My w10 system complains about *Error during sweep* *Stopped* *Failed to read data 1 10 times* *Data outside expected valid ranges, or in unexpected format.* *You can disable validation on the device settings screen.* This just happened in the last couple of days. I have both 0.3.7 and 0.3.8 on my W10 system and this problem exists on both saver versions. Help Fred - N4CLA On Thu, Dec 17, 2020 at 9:00?AM GM4OSS <stevegm4oss@...> wrote:
Hi |
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Re: S11 ? if Zc complexe
On 6/26/23 11:12 AM, Fran?ois wrote:
It's possible, that with some active systems, you could get a reflectionWe have a little trouble understanding each other. It is not a question of measurement but of calculation. Indeed.. For instance if Z1 = 2 - 1000j and Z2 is 50 + 100j, then gamma = (Z1-Z2)/(Z1+Z2) gamma = 1.215 - 0.124j |gamma| > 1 (and it's not some sort of numerical precision thing) OK, we must have some interpretation problem. And it's not obviously "unphysical" - I can see a source with Z 50 + 100 j (A series inductor) and a load of 2-1000j (a series capacitor). Sure, it's not a conjugate match, but obviously power will be dissipated in the 50 ohm resistor. So this must be a case where "reflection coefficient" as defined by impedances isn't correct. There's no real transmission line here, so I'm not sure that the concept of a "traveling wave" (where gamma is reflected/incident) is valid. |
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Re: Outliers in group delay measurement
Or is the best path forward just tocan you send as attachment your .s2p file I wrote a little software to smooth out the errors. I would see what happens. -- F1AMM Fran?ois De la part de astech119 Envoy¨¦ : lundi 26 juin 2023 18:32 |
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Re: S11 ? if Zc complexe
It's possible, that with some active systems, you could get a reflectionWe have a little trouble understanding each other. It is not a question of measurement but of calculation. I have an adapter which for a given input impedance returns the impedance Zout = 1.96593624236642 -j 5601.37911926951)} The impedance I'm targeting is Ztarget = 50 +j 100 the results are recalculated in the Excel sheet attached S11 = 1.03617959022359 -j 0.0185190120640808 SWR = -56.028101163433028 negative |S11| = 1.036345067 -> |S11| > 1 -- F1AMM Fran?ois De la part de Jim Lux lundi 26 juin 2023 16:58 |
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Outliers in group delay measurement
I'm measuring the group delay of some 60in cables with a NanoVNAH4 and I am getting outliers in the data. I am using nano-vna saver and I have tried both with on board calibration disabled and calibrated from 50kHz to 1.5GHz, the outliers are present still. I also have another H4 and I had the same issue just at a lower frequency ~150MHz. In the attached plot the points go to about +- 20 ns at just under 700MHz. I have also changed the sweep to have a lower df width but the same outliers were there at the same frequency. My sweep here is 1Mhz to 701Mhz 1212 pts 3avg df=578kHz
Is there any explanation or way to minimize this? Or is the best path forward just to remove the outliers manually when processing the data. Thanks! |
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Re: Inductor model
On Mon, Jun 26, 2023 at 01:23 AM, Mike wrote:
Calibrating with the crocodile clips will not give you a good reference plane. The reason I say this is if you keep them the same distance apart when you cal with an open, short and load you will have considerable inductance in the short and 50 ohm "cal loads". If you calibrate with the clips close together and then spread them the reference plane has changed. Neither is a good option. I suggest you calibrate right at the screw terminations on the green block with the alligator clip leads removed. Then attach the leads and make your measurement. From the photo it looks like the leads are about 4" long and each one will add about 100 nH of inductance (total 200 nH or 0.2 uH). That extra .2 uH when you are measuring 110 uH is not significant. However you should get a better estimate of the SRF and be able to calculate the parasitic capacitance to more accuracy. Try it and see what you find... Roger |
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Re: S11 ? if Zc complexe
On 6/26/23 7:26 AM, Fran?ois wrote:
I knew about the phone lines. My problem is that if we calculate the S11 with complex values, it leads, for example, to a ROS which can be negative. S11 is no longer in a circle of radius 1.It's possible, that with some active systems, you could get a reflection that is bigger than the incident wave (i.e. if the Zload were negative). But I think that for an entirely passive load, the reflected wave cannot be greater than the incident wave. |
Roger Need
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