Re: measuring Capacitance or Inductance
On Fri, Mar 19, 2021 at 12:40 PM, Gary W9TD wrote:
Do you import the s2p from the NanoVNA then to analyze and plot?
Gary
W9TD
Yes, except in this case I'm making a 1 port s11 measurement with the nanoVNA. I use a very basic s1p data dump tool I wrote in VB and then I import the dumped s1p file into Genesys for analysis. It just takes a few seconds to do it all as I have an inductance template in Genesys for this type of analysis.
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Re: measuring Capacitance or Inductance
Here's a nanoVNA-H measurement of a Micrometals T50-6 powdered iron toroid with 22 turns spread over about 270degrees of the toroid. The inductance should be about 2.2uH and you can see the nanoVNA does a good job again. It also has a reasonable stab at measuring the series resistance although the data gets a bit noisy above 20MHz. I keep meaning to add averaging to my PC tools. The nanoVNA is much more powerful than a typical low frequency LCR meter because it can measure the inductance across a wide frequency range. The inductance at the design frequency can usually be measured quite accurately. It often manages to give a reasonable estimate of Q for powdered iron toroids like this.
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Re: measuring Capacitance or Inductance
Do you import the s2p from the NanoVNA then to analyze and plot?
Gary
W9TD
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Re: measuring Capacitance or Inductance
I'm using Eagleware Genesys. This is old RF CAE software from 2004. I've had my nanoVNA-H for quite a while now and measuring the inductance of coils across LF through about 50MHz is what I mostly use it for. It can also give a fairly good indication of the coil Q as long as the Q of the inductor isn't too high.
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Hi all,
My name is Phil, and call is GU0SUP.
I am a new user of 2.8" nanoVNA, and I can calibrate it fine using the screen. However, when I start nanoVNA-Saver,set the start & stop frequency limits, I am able to click on the various calibrate options, and it says 101 points, but when I click on apply, it tells me "Two of short, open and load returned the same values at frequency 3600000Hz".
This is despite the fact that I have set the frequency range to the 2m band.
Where have I gone wrong? I can't seem to find any instructions, although I assume they must be somewhere...
Any help or pointers would be much appreciated.
Best 73
Phil GU0SUP
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Re: measuring Capacitance or Inductance
Jmr
What are you using to make your plots?
Gary
W9TD
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Re: measuring Capacitance or Inductance
To test out my nanoVNA-H over LF to about 50MHz I dug out a SMD airwound inductor of just over 240nH. I measured it in three ranges and stitched the results together to allow a log plot from about 100kHz to 50MHz.
The results below are quite good I think. The nanoVNA struggles a bit at 100kHz but from about 500kHz onwards the nanoVNA does a very good/stable job of measuring the inductance of the SMD coil and the red series resistance trace looks good too with a fairly smooth response across the frequency range. The resistance trace starts to misbehave a bit above 35MHz but this is a very good result for a low cost VNA.
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when the Nano VNA (connected to Nano Saver) first powers up, the sweep is 50KHz to 3 GHz. I have an antenna connected to port 1. I change the sweep to 900 to 930 MHz and click on Set Reference Sweep, but the graphs still display the default frequencies: 50 KhZ TO 3 GhZ. How do I get the graphs to display same frequencies as the sweep ?
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Nano Saver errors off in Calibration
I can calibrate my VNA manually, but I would prefer to calibrate using Nano Saver with my PC since the manual version does not include Isolation test.
When I have completed short, open, load, isolation and thru, I click on "APPLY" the program disappears from my Windows 10 PC.
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Re: NanoVNA measurement of an EFHW Transformer
Thanks to everyone's input - I was able to get things sorted out. I actually tried both methods (Back to Back Method - thanks to Gary and the resistor method - thanks to Roger and found reasonable agreement. I also compared it with the insertion loss calculated using the Fair-rite 43 permeability values which can be found in Owen Duffy's Blog 43 Ferrite for a 3 turn primary. Interestingly, the computed value is smack in between the resistor method -0.44 dB at 3.5 MHz and the Back-to-Back Method at -.75 dB. The calculated value using the Duffy calculator and the permeability values which ignores flux leakage and conductor losses provides a result of -0.61 dB at 3.5 MHz. This leads me to think that the back to back approach might be more conservative. The comparison plot from both methods is attached. Ariel NY4G ?On 3/18/21, 4:57 PM, " [email protected] on behalf of Gary W9TD" < [email protected] on behalf of w9td@...> wrote: Ariel, That would be satisfactory but your test fixture looks like ground is connected between inpuy and output anyway so connect to that grounds Gary W9TD
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Re: NanoVNA measurement of an EFHW Transformer
Ariel,
That would be satisfactory but your test fixture looks like ground is connected between inpuy and output anyway so connect to that grounds
Gary
W9TD
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Re: NanoVNA measurement of an EFHW Transformer
Channel 0 is the source of RF energy. Channel 1 is the 'sink' or receiver
of that RF energy. Any 'source' requires a return. Without a return, it's
just a conductor flapp'n in the wind. What is launched out of the center
conductor of Channel 0 SMA returns against the backshell and the 'innards'
of the VNA. Absolutely *yes*, the return (ground) of the energy on the
center pin of the Challen 0 source must be returned to the chassis or
backshell of the Channel 0 connector!
In your ham station, you wouldn't connect only the center pin of the
PL-259! Same for the NANOs.
Dave - W?LEV
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On Thu, Mar 18, 2021 at 4:56 PM Ariel NY4G <ny4g@...> wrote: Gary W9TD
Thanks for your input - on that. The grounds are together but not
connected to any of the grounds. Should I connect it to the CH0 ground?
Thanks
Ariel NY4G
On Mar 18, 2021, at 11:05, Manfred Mornhinweg <manfred@...> wrote:
?
Manfred, Have you ever compared the Q readings measured by the old
BRC-160 or
the Hp 4342 Q meters against the Q reported by any network analyzer or
even
many of the older 4 terminal instruments from the 70's and 80's and
maybe into
the 90's? No, I haven't, because I don't own any of those old meters. At work we
did have a big HP VNA that went up to a glorious 13MHz, but I didn't have a
NanoVNA to compare to that, in 1990...
The old Q meter uses a parallel resonant circuit technique and
this was considered the best method until technology caught up. I normally measure the Q of inductors by resonating them with a high
quality capacitor and measuring the resulting bandwidth. For many years I
did this using a grid dip meter, and nowadays I do it with other devices,
including the NanoVNA. But this technique is based on the assumption that
the capacitor's Q is so much higher than that of the inductor, that the
total Q measured is close to the inductor's Q. This technique cannot be
applied to measuring the Q of capacitors, because sufficiently good
inductors don't exist. An inductor Q of around 10000 to 50000 would be
required, depending on the quality of the capacitor to me measured!
Which brings up the idea of measuring a capacitor's Q by resonating it
with a quartz crystal... With some care, that might be workable in some
cases. Measuring the impedance curves of the crystal alone, then with the
capacitor in series, and then doing the maths.
But I would like a simpler method, that displays a curve of the
capacitor's Q over frequency. The crystal method can't do that. An
extremely good VNA should be able to do it.
Manfred
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: NanoVNA measurement of an EFHW Transformer
Gary W9TD
Thanks for your input - on that. The grounds are together but not connected to any of the grounds. Should I connect it to the CH0 ground?
Thanks
Ariel NY4G
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On Mar 18, 2021, at 11:05, Manfred Mornhinweg <manfred@...> wrote:
?
Manfred, Have you ever compared the Q readings measured by the old BRC-160 or
the Hp 4342 Q meters against the Q reported by any network analyzer or even
many of the older 4 terminal instruments from the 70's and 80's and maybe into
the 90's?
No, I haven't, because I don't own any of those old meters. At work we did have a big HP VNA that went up to a glorious 13MHz, but I didn't have a NanoVNA to compare to that, in 1990...
The old Q meter uses a parallel resonant circuit technique and
this was considered the best method until technology caught up. I normally measure the Q of inductors by resonating them with a high quality capacitor and measuring the resulting bandwidth. For many years I did this using a grid dip meter, and nowadays I do it with other devices, including the NanoVNA. But this technique is based on the assumption that the capacitor's Q is so much higher than that of the inductor, that the total Q measured is close to the inductor's Q. This technique cannot be applied to measuring the Q of capacitors, because sufficiently good inductors don't exist. An inductor Q of around 10000 to 50000 would be required, depending on the quality of the capacitor to me measured!
Which brings up the idea of measuring a capacitor's Q by resonating it with a quartz crystal... With some care, that might be workable in some cases. Measuring the impedance curves of the crystal alone, then with the capacitor in series, and then doing the maths.
But I would like a simpler method, that displays a curve of the capacitor's Q over frequency. The crystal method can't do that. An extremely good VNA should be able to do it.
Manfred
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Re: NanoVNA measurement of an EFHW Transformer
No problem Manfred. I have two of the old Boonton Radio Corp Q meters. HP acquired Boonton and continued the line with the hp4342 which is still in use where I worked until last June.
Here's the method I tried to explain above to measure EFHW transformer loss. Only one transformer is needed. Replace the Sig Gen and the power meter with the Nanovna between ch0 and ch1.
This was long before I had the Nanovna which I finally purchased in Aug 2019. The 6 dB pad's didn't make much of a difference with the Nanovna in use.
I also used a SLMS (selective level measuring set that was used by the old analog telephone systems. It has a tracking generator and a very very accurate receiver). I Sorry...one last instrument. I used the old HP 415 Square law SWR meter with a diode detector for the power level indicator. No one in the ham radio community knows what these are and they were very cheap at hamfests.
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Re: NanoVNA measurement of an EFHW Transformer
Manfred, Have you ever compared the Q readings measured by the old BRC-160 or
the Hp 4342 Q meters against the Q reported by any network analyzer or even
many of the older 4 terminal instruments from the 70's and 80's and maybe into
the 90's? No, I haven't, because I don't own any of those old meters. At work we did have a big HP VNA that went up to a glorious 13MHz, but I didn't have a NanoVNA to compare to that, in 1990... The old Q meter uses a parallel resonant circuit technique and
this was considered the best method until technology caught up. I normally measure the Q of inductors by resonating them with a high quality capacitor and measuring the resulting bandwidth. For many years I did this using a grid dip meter, and nowadays I do it with other devices, including the NanoVNA. But this technique is based on the assumption that the capacitor's Q is so much higher than that of the inductor, that the total Q measured is close to the inductor's Q. This technique cannot be applied to measuring the Q of capacitors, because sufficiently good inductors don't exist. An inductor Q of around 10000 to 50000 would be required, depending on the quality of the capacitor to me measured! Which brings up the idea of measuring a capacitor's Q by resonating it with a quartz crystal... With some care, that might be workable in some cases. Measuring the impedance curves of the crystal alone, then with the capacitor in series, and then doing the maths. But I would like a simpler method, that displays a curve of the capacitor's Q over frequency. The crystal method can't do that. An extremely good VNA should be able to do it. Manfred
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Re: NanoVNA measurement of an EFHW Transformer
Arien, What am I doing wrong? The chart I plotted from the nanoVNA into Excel just
does not look right. It actually looks quite right to me! I wouldn't expect anything else. The parasitics of your system (stray capacitance of those large windings, series inductance of the long connection wires, leakage inductance of those poorly coupled transformers) are combining to give your transformers a very marked lowpass behavior. Core loss might be adding to it, but I would suspect that most of that large insertion loss is simply mismatch loss caused by all those parasitics. If so, it should be possible to tune it out, at least for a single frequency, by adding the proper compensation components. Manfred
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Re: measuring Capacitance or Inductance
Thank you Garry for the explanation. It is clear now.
Slawek
SP9BSL
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Re: NanoVNA measurement of an EFHW Transformer
Ariel,
I cannot see for sure but the common ground off on the left side doesn¡¯t look like it is connected to NanoVNA ground. It needs to be.
Gary
W9TD
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Re: measuring Capacitance or Inductance
Slawek,
The inductance is in series with the capacitance and as you approach series resonance the net impedance drops and if it is still below the resonance, the effect is a lower capacitive reactance which is equivalent to a larger capacitance.
Gary
W9TD
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Gary W9TD
Phil Cooper
ariel.jacala
