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Author Topic: Smudge proposed NMR experiment replication.  (Read 12804 times)

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With the small balun i have a 3V 1.6µs pulse on the secondary.
A large inductance transformer is needed only for transferring pulses, which have a looong rise time (or fall time), i.e.: slow analog signals.
With digital signals, the short pulse appearing across the secondary winding of small transformers affects only the output amplitude of the passive pulse stretcher.  It does not affect the output of the active pulse stretcher.
   

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Ok, so what would be the preferred balun for the NMR input setup, the small one or the large Smudge one?
Both galvanically isolate, but does the small one also change from balanced to unbalanced?
I would go with the small one because it has a smaller interwinding capacitance and the signal frequency is high enough that the low inductance of the small one does not matter. Also, the current is so low now, that there is no chance of saturating the core. If you ever go to higher current levels then a larger core will be needed (but not a larger inductance).
For the isolation of digital signals I would also use the small one but with a pulse stretcher so I can see the signal clearly on the scope when the sweep times are long (I have an ext.Trig input, so I could do without the stretcher).

P.S.
If I were you, I would rewind the coils (with Litz wire) so they are symmetric in themselves and do not need to be concerned with the hot/cold side issue and don't have any unbalanced longitudinal currents ...but that is only what I would do.  The author might disagree.
   

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Ok, thanks,  i put up my balun made yesterday (https://vk6ysf.com/balun_1-1.htm) which i know is not isolating, but does unbalance/balance on the input side before the caps.

It minimzes the input signal on the pancake coils though.
It went from 24Vpp to now about 10Vpp while i increased the FG signal from 10Vpp to 20Vpp.

Sweeping from 3 to 5Mhz still.

So we lose a lot of signal using the balun.


Concerning your P.S., sounds sound to me, but what do you mean by "so they are symmetric in themselves"?
How can i wind a pancake coil to be symmetric in itselve?

Itsu
   

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How can i wind a pancake coil to be symmetric in itself?
For example like this:
« Last Edit: 2020-07-11, 02:17:02 by verpies »
   

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Hmmm,   that is neat,  never saw that one before   O0

   

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Seems i am unbanned as i have fast access again to OUR without using the proxy.


I have tested the severall baluns i have, and the best one (least signal loss) is the big one Smudge was refering to earlier.

But even this one has about 66% signal loss compared to the no balun situation (12V v 39V).
Also there is no difference percentage wise in input v output signal in resonance.

With balun i have 12V input and 8V output (33%).
Without balun i have 39V input and 25.6V output (33%) see screenshot.

So it seems to me that using a balun is not helping the avoid the crosstalk and only adds losses to the system.

Itsu
   

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Seems i am unbanned as i have fast access again to OUR without using the proxy.
It is my experience that the ban times-out when there is not activity from the banned IP.

But even this one has about 66% signal loss compared to the no balun situation (12V v 39V).
This is too much loss for a 1:1 transformer. Perhaps its ratio is not 1:1 and the impedance is getting transformed or the transformer introduces leakage inductance into the primary LC circuit and detunes it.
How does the transmission loss vs. frequency plot appear for this transformer, when you connect the TG's output to the primary and SA's input to the secondary ?

Also there is no difference percentage wise in input v output signal in resonance.
How do you measure that?

With balun i have 12V input and 8V output (33%).
Without balun i have 39V input and 25.6V output (33%) see screenshot.
What about the current flowing in the pancake coils?  The voltage at the caps is not very representative of the magnetic flux amplitude generated by the coils...

So it seems to me that using a balun is not helping the avoid the crosstalk and only adds losses to the system.
I am surprised, symmetrizing the input to the primary LC circuit should help a little.  Does galvanic isolation make any difference ?
   

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Quote
It is my experience that the ban times-out when there is not activity from the banned IP.

Yes, could be, but now it toke 2 days, the last time only 12 hours or so.





Quote
This is too much loss for a 1:1 transformer. Perhaps its ratio is not 1:1 and the impedance is getting transformed or the transformer introduces leakage inductance into the primary LC circuit and detunes it.
How does the transmission loss vs. frequency plot appear for this transformer, when you connect the TG's output to the primary and SA's input to the secondary ?

Its soldered to a little pcb now, so will do that tomorrow.

Quote
How do you measure that?

By looking at the FM sweep plots like the one in my last post, it shows the 39V in / 25.6V out = 33%
Another one not shown but with the balun shows in 12V / out 8V =33% too

 
Quote
What about the current flowing in the pancake coils?  The voltage at the caps is not very representative of the magnetic flux amplitude generated by the coils...

I will do a current pancake coil versus output signal (unloaded) per frequency step tomorrow.

Quote
I am surprised, symmetrizing the input to the primary LC circuit should help a little.  Does galvanic isolation make any difference ?


The Smudge balun is galvanically isolated, it has trifilar windings (2 layers) on a big toroid from which only 2 out of the 3 wires are used as isolation transformer, see here:
https://www.overunityresearch.com/index.php?topic=3847.msg78156#msg78156

its the first picture, the isolation xformer is the one on the left.


Itsu




   

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I will do a current pancake coil versus output signal (unloaded) per frequency step tomorrow.
Your secondary circuit is closed by the capacitance and resistance of the wire, so it is loaded ...albeit not deliberately.
It should be frequency-selective as any LCR circuit is.  Did you ever do a FM sweep of the secondary or just observed its frequency response through its reflection back to the primary ?
   

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No i did not sweep the secondary, will do that too.

The current through the pancakes is weak, around 5mA rms and very sensitive to tuning the mostly input trimmer cap.
It also is not "in sync" with the output voltage, so i will go for the max. current each time.

I will try to make a plot between 3 and 5Mhz.

Itsu
   

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It also is not "in sync" with the output voltage, so i will go for the max. current each time.
In theory, the voltage induced in an open-circuited secondary is proportional to the 1st derivative of current flowing in the primary (di/dt).
IOW: 90º off, because this is where the sine wave changes the fastest ( is the steepest ).
   

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Ok,  i will check on that 90° off situation.

Sweeping the secondary shows a flat response up till 60Mhz.
The 100pF parallel output cap seems to have no influence, also the input cap not.

The below screenshot shows a 1Khz to 10Mhz sweep of the secondary (toroidal) coil.

Itsu
   

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Sweeping the secondary shows a flat response up till 60Mhz.
The 100pF parallel output cap seems to have no influence, also the input cap not.
This is really weird!  Where do you apply and sense the signal during the sweep ?
Please remind me what is the inductance of the secondary.
   

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Yes, i found that weird too.

See picture for connections.

The toroidal coil measured 31uH

Itsu
   

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Quote
Quote
Quote from: Itsu on 2020-07-04, 20:17:01

    But even this one has about 66% signal loss compared to the no balun situation (12V v 39V).
This is too much loss for a 1:1 transformer. Perhaps its ratio is not 1:1 and the impedance is getting transformed or the transformer introduces leakage inductance into the primary LC circuit and detunes it.
How does the transmission loss vs. frequency plot appear for this transformer, when you connect the TG's output to the primary and SA's input to the secondary ?

Here first below the TG SA plot of the Smudge balun ALONE, 0 to 50Mhz.
Its fairly flat the first 10Mhz in which we want to use it.

Second plot is when TG's output to the primary and SA's input to the secondary including the Smudge balun (also 0 to 50Mhz).

Itsu

   

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Here first below the TG SA plot of the Smudge balun ALONE, 0 to 50Mhz. Its fairly flat the first 10Mhz in which we want to use it.
That's to be expected of a transformer which windings are in such intimate contact. It has 53.5% maximum transmission loss of the signal's amplitude up to 13.5MHz if you'd done the calibration apriori.
Why?  Because -6.65dB = 46.5% of the amplitude applied to the primary winding.
Let's see how it performs from 0Hz to 500kHz so I can correlate it with the other plot.  It is impossible that it has 0db transmission loss at 0Hz.


Second plot is when TG's output to the primary and SA's input to the secondary including the Smudge balun (also 0 to 50Mhz).
Did you do the SOLT calibration (flattening) with the balun and other interconnects in place before connecting the pancake and toroidal coils ?  Why do you have the 10dB attenuation at the SA's input on ?
Anyway, I'd like to see it zoomed in the frequency span between 0Hz and 4MHz. I think there is a -65dB dip to at 400kHz but I cannot see what's before that.

To have a complete picture, I'd also need a plot where the TG is connected to the input caps (the same as before), but the SA's input is connected to a good* CSR in series with the pancake coils (with the toroidal coil not connected and opened).  Sorry to be so demanding - I just care more about the current flowing in the pancake coils** than the voltage applied to their input caps. 

P.S.
Please use long sweep times so the coils have the time to settle. Mine were ringing for milliseconds, so the adjacent frequency points were affected by the coils still ringing from the stimulus at the previous f.point.

* "good" means low resistance and non-inductive. Its resistance should be as small as possible but not so small that the signal level across it approaches the internal noise level of the SA.
** I cannot write the same about the opened secondary side (the toroidal coil). Sensing the induced voltage across it, is representative of the magnetic flux variations it experiences.
   

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Quote
That's to be expected of a transformer which windings are in such intimate contact. It has 53.5% maximum transmission loss of the signal's amplitude up to 13.5MHz if you'd done the calibration apriori.
Why?  Because -6.65dB = 46.5% of the amplitude applied to the primary winding.
Let's see how it performs from 0Hz to 500kHz so I can correlate it with the other plot.  It is impossible that it has 0db transmission loss at 0Hz.


Ok, 1st screenshot is the Smudge balun from 0 (in fact from 9Khz = minimum) to 500Khz.
The 10dB attenuation at the SA's input is default, i now have removed it, so now at 0dB.




Quote
Did you do the SOLT calibration (flattening) with the balun and other interconnects in place before connecting the pancake and toroidal coils ?  Why do you have the 10dB attenuation at the SA's input on ?
Anyway, I'd like to see it zoomed in the frequency span between 0Hz and 4MHz. I think there is a -65dB dip to at 400kHz but I cannot see what's before that.

I normally always first before any measurement do the "normalisation" procedure using as much connections needed before hooking up the DUT, but i did NOT included the balun in this normalisation process, see 2th screenshot.
0 (9Khz) to 4Mhz, SA input 0dB.
I will redo this one including the balun in the normalisation procedure next.


The csr plot for the whole picture comes then......


Itsu
   

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This plot is with the Smudge balun included in the normalisation (flattened), 0 (9Khz) to 4Mhz and 0dB SA input.

Itsu
   

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This is a plot with the TG connected to the input caps (the same as before), but the SA's input is connected to a good* CSR in series with the pancake coils (with the toroidal coil not connected and opened).

csr is 10 Ohm 1% inductionfree in the pancake coils return lead.
SA connected across this csr, TG SA grounds together.

0 (9Khz) to 10Mhz, not shure how the afjust the sweeping times (RBW?)       EDIT   increased the sweep time from 11ms in the first screenshot to 10s in the 2th

Itsu
   

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0 (9Khz) to 10Mhz, not shure how the afjust the sweeping times (RBW?)
Yes,  "RBW" or "TrigSetup/Points". Some SAs also have an option "Delay Between Points".
   

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This is a plot with the TG connected to the input caps (the same as before), but the SA's input is connected to a good* CSR in series with the pancake coils (with the toroidal coil not connected and opened).
...
EDIT   increased the sweep time from 11ms in the first screenshot to 10s in the 2th
OK, this should illustrate to you that despite the TG injecting a CONSTANT VOLTAGE AMPLITUDE signal into the primary circuit, the current amplitude in the pancake coils is NOT constant.

Now, this function of pancake current amplitude vs. input voltage amplitude, must be used to modify the voltage Transmission Loss measurement, which you've already done. Can your SA export it in numeric form (e.g. csv) ...or do I have to count pixels ?

All of this is illustrated on the diagram below:
Our goal is to obtain the frequency characteristics of the Crosstalk Factor (red) in order to determine what is causing it (electric coupling, magnetic coupling or both...and how much of each).
Voltage does not create the magnetic field of the pancake coils - the current does.
But we can measure only the voltage Transmission Loss (blue), because our Signal Source (TG or FG) is a voltage source and it is located before the Input Matching Circuit, which has its own frequency characteristic.
Note, that I am disregarding the frequency characteristic of the output circuit at the toroidal winding - it is not even present on the diagram.
« Last Edit: 2020-07-05, 20:27:58 by verpies »
   

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OK, this should illustrate to you that despite the TG injecting a CONSTANT VOLTAGE AMPLITUDE signal into the primary circuit, the current amplitude in the pancake coils is NOT constant.

Well, it illustrates to me that we have resonance in the pancake coils around 4.1Mhz now viewed through that peak (being current).
Do you say that the current trace should be flat as it is now NOT flat (NOT constant)


Anyway,  here attached a CSV file from that trace. (its not zipped,  just remove the .zip and there you have the csv file)


Itsu
 
« Last Edit: 2020-07-05, 20:56:37 by Itsu »
   

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Do you say that the current trace should be flat as it is now NOT flat (NOT constant)
No, no, the pancake current amplitude of input voltage amplitude vs. frequency should not be flat in the input matching circuit.  It just means that the voltage induced across the secondary toroidal coil must be scaled down by the inverse of Pancake.i (Input.v)

Anyway,  here attached a CSV file from that trace. (its not zipped,  just remove the .zip and there you have the csv file)
Got it, but any scaling process involves at least two inputs...so I also need the "blue" measurement in the same frequency span and RBW as "fuchsia" measurement, which I just received from you in 1.csv.zip.
I used the fuchsia color to mark the pancake.i(input.v) measurement in the diagram below.
« Last Edit: 2020-07-05, 21:22:27 by verpies »
   

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OK,  here the "blue" measurement in the same frequency span and RBW:

Quote
Our goal is to obtain the frequency characteristics of the Crosstalk Factor (red) in order to determine what is causing it (electric coupling, magnetic coupling or both...and how much of each).


Ok, so by knowing the blue and fuchsia color data you can calculate the red data.


Itsu
   

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...in the same frequency span and RBW:
2.csv.zip
Nope, this one is with a different span and RBW. e.g. it starts from 0Hz and the fuchsia one started from 50kHz.  I could interpolate to fit them, but why introduce a numerical error...
   
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