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Author Topic: Smudge proposed NMR experiment replication.  (Read 44160 times)

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Low SWR is a general indicator of efficient energy transfer from the source to the load* (meaning: "low energy reflection coefficient"), but it is not an indicator of the maximum current flow in the coil.
Purely reactive components are perfect energy reflectors (by definition they have the reflection coefficient equal = 1 , the highest possible). They absorb the energy from the source and in the next quarter-cycle, they give it all back to the source, ...so the net energy transfer is zero over the entire cycle, but these circulating currents can be high, nonetheless.

Watch a guy using a sim to match a loop antenna using Smudge's capacitor network.
https://youtu.be/weNwZ0D3txg

* The pancake coils are not the load. If you put a solid copper sheet next to them, then the induced eddy currents will heat this sheet and present a load to the source. ...the precessing protons will, too.

OK,  so the best way to tune is to measure the current in the pancake coils and tune for max.
I tried something earlier, but with the magnets in place they influence the current probe, so will need to remove them.

That simsmith program looks great, will have to take a closer look at it.

Itsu
   

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Is this what you mean?
Yes, this is exactly what I had in mind.

If this Litz microloop behaves well below its resonance frequency (which should be pretty high because of its small size) and is linear, then you have a directional sensor of high frequency magnetic field.
This means that your measurements of the current flowing through the pancake coils (by CSR or i-probe) will not be skewed anymore by the current flowing in their intrawinding capacitances.
This way you will obtain a more realistic picture what is going on in these coils.
   

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I will seriously consider to buy one.
In that case, beware of the many fakes/clones out there and also watch this review of that NanoVNA:
https://youtu.be/fSzY5q-QTpw
   

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OK,  so the best way to tune is to measure the current in the pancake coils and tune for max.
Better yet, measure the amplitude of the magnetic field generated by the pancake coils using your new Litzed i-Probe (no pun intended) with the proper orientation.
This way the current flowing in the pancake's intrawinding capacitance will not deceive you.

The only way you can go wrong with this magnetic method is if:
  • the Litz loop is nonlinear (e.g. skin effect)
  • the Litz loop is too close to its SRF (but that frequency should be very high for such a small loop)
  • the i-Probe's internal DC compensation circuit gets overloaded

I tried something earlier, but with the magnets in place they influence the current probe, so will need to remove them.
Yeah, the magnets saturate the magnetic core in the probe and the internal DC compensation circuit cannot cancel that level of external magnetic flux density from the magnets.
My i-Probe even has a red LED that lights up when that happens.
« Last Edit: 2020-07-20, 14:16:45 by verpies »
   

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Bonus rant below (not necessarily for Itsu):

In most daily Ham experiences the AC electric energy provided by the signal source (FG, SG, oscillator, exciter, RF Amplifier) gets permanently converted to:
  • heat
  • mechanical kinetic energy
  • radio waves.

The heat leaves the system and transfers to the environment. See: Joule Heating and Inductive Heating and Electric/Dielectric Heating.
Ampere forces between wires and electric forces as well as piezoelectrcs can cause acoustic vibrations of wires and other components.
The radio waves separate from the material radiator (antenna) and move outward away from it at the speed of light*.  See: Radiation Resistance.

This conversion of energy is necessary for us to be able to define a load and the energy transfer to that load.
An ideal reactive component (capacitor, inductor) does not convert the energy from the source permanently. It merely stores it temporarily and then gives it all back to the source. So, an ideal reactive component cannot be a "load" unless it radiates radio waves into the far-field ( near-field E or H fields do not separate from the "radiator", thus their energy is recoverable and no permanent energy conversion occurs. IOW: The generation of Near Fields by reactive components does not count as permanent energy conversion ! )

In this entire endeavor (this thread) we are trying to convert the AC electric energy from the source into a fourth form of energy - the energy of proton's precession**, and to detect this energy.
This is a different form of energy from the three listed above.  This difference is an exciting stuff in itself.

* For Centralflow: ...or matter moves inward away from the photons at the speed of light.
** Of course the proton precession energy eventually gets converted to heat through spin relaxation.
« Last Edit: 2020-07-12, 13:54:23 by verpies »
   

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In that case, beware of the many fakes/clones out there and also watch this review of that NanoVNA:
https://youtu.be/fSzY5q-QTpw

That nanoVNA-F (10Khz-1.5Ghz) with the bigger screen looks perfect for me considering my age.




Better yet, measure the amplitude of the magnetic field generated by the pancake coils using your new Litzed i-Probe (no pun intended - I hate Apple Inc.) with the proper orientation.
This way the current flowing in the pancake's intrawinding capacitance will not deceive you.

The only way you can go wrong with this magnetic method is if:
  • the Litz loop is nonlinear (e.g. skin effect)
  • the Litz loop is too close to its SRF (but that frequency should be very high for such a small loop)
  • the i-Probe's internal DC compensation circuit gets overloaded
Yeah, the magnets saturate the magnetic core in the probe and the internal DC compensation circuit cannot cancel that level of external magnetic flux density from the magnets.
My i-Probe even has a red LED that lights up when that happens.

OK, i will try that, but lets take one step back.

you said earlier:

Quote
Low SWR is a general indicator of efficient energy transfer from the source to the load* (meaning: "low energy reflection coefficient"), but it is not an indicator of the maximum current flow in the coil.

Surely there must be a way to have the best of both worlds, meaning a good match from the PA to the pancake input circuit (resistive) and max. current in the pancake coils itselve (reactive).
I found a good article covering the feedline coupling too here:
https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm



Thanks for the rant, it contains great info like on Radiation Resistance.

Itsu
   

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Buy me a beer
Itsu

Don't you have an antenna matching unit for HF, a small ferrite Toroid, pass the wire which connects the two pancake coils through the Toroid and wind 2 turns of wire through the Toroid and connect to the matching unit. You should get full power into the coils and no reflection back to source, just my 2 pence worth.

Regards

Mike


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In reply to Verpies rant, may I offer my own rant.
Quote
.........................In this entire endeavor (this thread) we are trying to convert the AC electric energy from the source into a third form of energy - the energy of proton's precession**, and to detect this energy.

I would not use the word "convert".  Conversion of one form of energy into another brings in the whole thorny concept of CoE.  I would say that in this endeavour we are trying to use the AC electrical energy of the source to enable energy to be extracted from the perpetual precession motions of the protons.  I think this "conversion" aspect comes from the quantum mechanical approach where you define the splitting of energy levels (see image below) which doesn't convey the actual precession motion of the spinning nucleus.  I come from the old school where I believe the nucleus does actually spin and precess, that precession motion exists and is perpetual but is so random between atoms that it does not create observable signals.  Yes you need to apply energy in order to see a signal, and certainly in the usual pulsed NMR experiments the quantum mechanical approach supplies the answer for the needed energies.  But if the precession motions are perpetual and our energy input has merely taken away the randomness, why can't we keep this cohered state going forever and continually extract energy from those precessions?  Ramsey's observations some 70 years ago suggests this may be possible.  That then begs the question, why in the last 70 years has no one followed this up or found out how to do it?  I think this may be due to the classical NMR experimental approach using solenoidal coils where the material sample containing the nuclei under investigation is within that coil.  The scientists use "filling factor" to define the volume of the sample in relation to the volume of the solenoid.  At 100% filling factor it is assumed that this gives maximum coupling between the sample and the coil.  However those of us skilled in the art know that, if we treat the sample as a form of magnetic core, that core will suffer a demagnetization effect.  The only way to eliminate such demagnetization is by use of very long thin solenoid-plus-cores, or the use of ring cores with toroidal windings.  The former leads to problems in maintaining the uniformity of the crossed static field along the length of the solenoid, and as far as I know no one has attempted the use of the ring core approach.  The cylindrical symmetry of the static field from disc magnets offers uniformity of the crossed field throughout the ring sample, and the toroidal coil offers maximum coupling with no demagnetization effects.
         
Quote
This is a different form of energy from the two listed above.  This difference is an exciting stuff in itself.

Yes, and if we achieve OU we know where the anomalous energy comes from

Quote
** Of course the proton precession energy eventually gets converted to heat through spin relaxation.

That is true for pulsed NMR, but note that there are two relaxation times.  The thermal relaxation is much longer than the dephasing relaxation.  I think that CW operation offers the possibility that, after the initial switch-on absorption-energy has got  the precessions cohered, the continued absorption energy rate needed to keep the phasing intact is lower than the radiated power extracted.

Smudge
   

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I would not use the word "convert".  Conversion of one form of energy into another brings in the whole thorny concept of CoE.
I could agree with that when it comes to nuclear dynamic but when doing RF engineering, the notion of permanently converting the AC energy into something else is important, because if that conversion is not done, then the transmitting coil is just going to store this energy for the quarter of the AC cycle and return it all back to the source later.
When this happens, a large energy reflection is perceived by the source ( the "reflection coefficient" (Γ) approaching 1 ...and SWR approaching infinity ).  This upsets the RF amplifier and its owner.

Of course, if the H-field generated between the coils does some work, i.e. on the nuclear spins, then the part of the energy used to do that work, does not get reflected back to the source ...and the reflection coefficient (Γ) improves ( as does the SWR, which is just equal to 1+│Γ│ / 1-│Γ│ ).

However, when the nuclei do not absorb the energy coherently because the owner of the RF amplifier is tuning the system off nuclear resonance, he can expect to have a "good match" (low Γ) only when the wiring's resistance* dissipates the AC energy as heat or the pancake coils efficiently convert this energy into far-field EM radiation.
Do we really want that ?

I come from the old school where I believe the nucleus does actually spin and precess, that precession motion exists and is perpetual but is so random between atoms that it does not create observable signals. 
I applaud your mechanistic approach to nuclear dynamics.  I also think the contemporary approach is too abstract.

But if the precession motions are perpetual and our energy input has merely taken away the randomness,
Very well

why can't we keep this cohered state going forever and continually extract energy from those precessions?  Ramsey's observations some 70 years ago suggests this may be possible.
Perhaps because nucleus cannot exist without these spins** and if you cancel them, it will fall apart into simpler particles/motions: proton into muon, muon into electron, electron into photon. But no worry, that is still "energy extraction".
My unorthodox view is, that it is possible to have motion without an object*** (since motion is merely a relation between space and time [s/t] ).  Thus an object/particle is just a spun up space and these particles, I've just mentioned, as well as nuclei, are just mere motions, which can be cancelled by other opposing motions.

That then begs the question, why in the last 70 years has no one followed this up or found out how to do it?
Because not many try what is though to be impossible.

* and RF amplifier's internal resistance.
** because the nucleus consists of these spins
*** Mainstream science treats objects axiomatically.  On the basic level it does not define what makes an object an object. Sometimes it attempts to define its properties, such as: a definite spatial boundary or spatial coordinate (but not always, see: "wave-particle duality") or mass (but only for physical objects such as a collection of gravitating matter or single gravitating massive particles - not for photons though), or just "anything that exists" and is "separate from the background".  And when you ask: "What "background" ? - the mainstream science replies: "Well, the spatial background, of course". Then you ask: "So is this `spatial background` another object ?", and the usual reply is: "No, of course not". Then you ask: "So if the `spatial background` is not an object then how can it exist?", then they usually flip and change their mind: "No, no, spatial background is an object", then you ask "How can it be an object if the prerequisites for an object existence is a spatial boundary and coordinate or mass or the general separateness from the background ?"...and round and round it goes.
« Last Edit: 2020-07-12, 14:51:43 by verpies »
   

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...an antenna matching unit for HF, a small ferrite Toroid, pass the wire which connects the two pancake coils through the Toroid and wind 2 turns of wire through the Toroid and connect to the matching unit. You should get full power into the coils and no reflection back to source, just my 2 pence worth.
What is going to happen to the energy provided by the RF amplifier?  Is it going to get absorbed by the "antenna matching unit" ?
   

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Surely there must be a way to have the best of both worlds, meaning a good match from the PA to the pancake input circuit (resistive) and max. current in the pancake coils itselve (reactive).
But "good match" in Ham terms means no energy reflection back to the source (i.e. low "reflection coefficient" (Γ) and low VSWR). This also means, that an efficient and permanent energy conversion must take place from the AC energy to something else.  If the near H-field generated by the coils does not perform any work and does not create any far-field EM waves (which permanently detach from the coil), then how are you going to get that permanent conversion?  ...and if you do not convert this AC energy to something else, the coil is just going to store it and feed it back to the source in the next quarter cycle, (because energy cannot be destroyed).

I found a good article covering the feedline coupling too here:
https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm
That is a good article that aims to maximize far-field EM radiation from a loop antenna.
But our goal is to create the maximum near-field magnetic field (H-field) between two loops - not to create a maximum far-field EM radiation.
Do these two maxima coincide ?
   

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Ok, so i understand that we are pumping RF into the pancake coils, but it cannot do anything with it:

Quote
If the near H-field generated by the coils does not perform any work and does not create any far-field EM waves (which permanently detach from the coil), then how are you going to get that permanent conversion?  ...and if you do not convert this AC energy to something else, the coil is just going to store it and feed it back to the source in the next quarter cycle, (because energy cannot be destroyed).

I think my mind cannot grasp this, as to me it is then pointless to try.

This "maximum near-field magnetic field (H-field) between two loops" surely needs some power to be build up, won't that power need to be fed in by the PA as efficiently as possible?

 
Edit:
reading somewhat further back you say:

Quote
Of course, if the H-field generated between the coils does some work, i.e. on the nuclear spins, then the part of the energy used to do that work, does not get reflected back to the source ...and the reflection coefficient (Γ) improves ( as does the SWR, which is just equal to 1+│Γ│ / 1-│Γ│ ).

So does this mean that ONLY at the moment "the H-field generated between the coils does some work etc...." this will be seen as a dip in the reflection coefficient and SWR?
If so, then there needs to be the focus on during the tuning i think.


Itsu
   

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Ok, so i understand that we are pumping RF into the pancake coils, but it cannot do anything with it:

I think my mind cannot grasp this, as to me it is then pointless to try.

This "maximum near-field magnetic field (H-field) between two loops" surely needs some power to be build up, won't that power need to be fed in by the PA as efficiently as possible?

 
Itsu

In my mind we need a certain value of H field or B field and that has an energy density.  Thus we must supply the total energy of that field integrated overall space, which essentially means the space occupied by the near field.  Our sample of protons does not absorb that total energy (it does not kill the field), so we get back most of that energy each half cycle.  That is why we need a tuning capacitor so that the returned energy then gets stored and recycled.  The matching network has to isolate the amplifier from that back and forth flow of energy between L and C while allowing the amplifier to supply only the energy lost each cycle.  I don't see that as a problem, but you must remember that my formative years were before the semiconductor revolution, I was brought up using vacuum tubes.  Yes, if you got a mismatch the anodes glowed red hot (a good warning sign!), but the tubes survived.  I am sure there must be ways to prevent poor SWR from damaging modern PA's.

Smudge
   

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I could agree with that when it comes to nuclear dynamic but when doing RF engineering, the notion of permanently converting the AC energy into something else is important, because if that conversion is not done, then the transmitting coil is just going to store this energy for the quarter of the AC cycle and return it all back to the source later.
When this happens, a large energy reflection is perceived by the source ( the "reflection coefficient" (Γ) approaching 1 ...and SWR approaching infinity ).  This upsets the RF amplifier and its owner.

Of course, if the H-field generated between the coils does some work, i.e. on the nuclear spins, then the part of the energy used to do that work, does not get reflected back to the source ...and the reflection coefficient (Γ) improves ( as does the SWR, which is just equal to 1+│Γ│ / 1-│Γ│ ).

However, when the nuclei do not absorb the energy coherently because the owner of the RF amplifier is tuning the system off nuclear resonance, he can expect to have a "good match" (low Γ) only when the wiring's resistance* dissipates the AC energy as heat or the pancake coils efficiently convert this energy into far-field EM radiation.
As I see it the at nuclear resonance the nuclei absorb only a small portion of the total field energy, so we need LC resonance to recycle the large quantity of unused energy.  And I think it likely that at this early stage the small portion of energy absorbed will be over-shadowed by a larger portion of energy lost to the coil resistance.  Thus the system will be well matched to that resistive loss which does not have an absorption peak, so I don't see the problem in the same way that you do.

Smudge
   

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What is going to happen to the energy provided by the RF amplifier?  Is it going to get absorbed by the "antenna matching unit" ?

Well you know it is not going to do that, so why ask!!!!!!!!!!

 It matches the complex impedance of the transmitter to that of the input end of the feedline. The input impedance of the transmission line will be different from the characteristic impedance of the feedline if the impedance of the antenna on the other end of the line does not match the line's characteristic impedance. The consequence of the mismatch is that the line's impedance (voltage to current ratio and phase) will oscillate along the line, or equivalently, raise out-of-phase voltage standing waves and current standing waves along the feedline.

I can see you don't want me here so I am gone, I have more important things to do with what time I have left in my life, you are a very condescending person and I think you need to stand back and look into that, your views are not everyone's as are not mine.

By the way of a compliment, your English is very good for eastern Europe.

Regards

Mike 8)


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Quote
In my mind we need a certain value of H field or B field and that has an energy density. 
Thus we must supply the total energy of that field integrated overall space, which essentially means
the space occupied by the near field. 
Our sample of protons does not absorb that total energy (it does not kill the field), so we get back most of that energy each half cycle. 
That is why we need a tuning capacitor so that the returned energy then gets stored and recycled. 
The matching network has to isolate the amplifier from that back and forth flow of energy between L and C while allowing the amplifier to supply only the energy lost each cycle. 
I don't see that as a problem, but you must remember that my formative years were before the semiconductor revolution, I was brought up using vacuum tubes. 
Yes, if you got a mismatch the anodes glowed red hot (a good warning sign!), but the tubes survived. 
I am sure there must be ways to prevent poor SWR from damaging modern PA's.

Smudge


Thanks Smudge,

so i take that as that you agree with what verpies is saying that energy is sloshed back and forth ("so we get back most of that energy each half cycle.")

These modern PA's are able to cope with bad SWR as their power is being regulated back.




Thanks Mike,

it seems you, like me, have a hard time grasping that the PA is unable to deliver any power to the circuit as nothing is radiated or consumed in the "no tuned" situation.

No "matching unit" is able to change that, so the PA gets overloaded if no precausions are followed.

So caution is needed in the no tune situation untill the effect we are after is revealing itselve.

Itsu   
   

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Well you know it is not going to do that, so why ask!!!!!!!!!!
To provoke a discussion about the fate of energy provided by the source.

You are a very condescending person and I think you need to stand back and look into that
Yes, I do not have the best social skills but notice, that I never use Ad Hominem remarks.
Also, I know what I am talking about technically and my mind is flexible enough that you can change it with logical arguments.

By the way of a compliment, your English is very good for eastern Europe.
Thank you, but that is also an Ad Hominem remark, ...even if a positive one.

I can see you don't want me here so I am gone,
You are mistaken, I do want you here (minus the Ad Hominem remarks).

It matches the complex impedance of the transmitter to that of the input end of the feedline. The input impedance of the transmission line will be different from the characteristic impedance of the feedline if the impedance of the antenna on the other end of the line does not match the line's characteristic impedance. The consequence of the mismatch is that the line's impedance (voltage to current ratio and phase) will oscillate along the line, or equivalently, raise out-of-phase voltage standing waves and current standing waves along the feedline.
What you wrote above is all true, but you did not answer the question about the fate of energy supplied by the PA.
« Last Edit: 2021-09-16, 16:19:47 by verpies »
   

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I made some tests using the I-probe.

Seems the best pickup is with the curved loop parallel to the pancake coil windings.

Max signal in the middle of the 11 turns.

Video here: https://www.youtube.com/watch?v=ijSGoCanuEM

Itsu
   

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I think my mind cannot grasp this, as to me it is then pointless to try.
Oh no, no - don't you give up.

This "maximum near-field magnetic field (H-field) between two loops" surely needs some power to be build up, won't that power need to be fed in by the PA as efficiently as possible?
Your statement is correct* but only in reference to a constant level of magnetic flux or a coil supplied with DC.
The answer to your question at the end is "yes" but only for a constant level of magnetic flux or for the 1st quarter of the AC cycle.

What you are failing to consider is what happens AFTER the magnetic field has been built up to its maximum level in the 1st quarter of the AC cycle.

When you do that, it will become apparent that in order to maintain the oscillation, this magnetic energy needs to be decreased back to zero. This can be done either by converting it back to electric current and dissipating its energy as heat in some resistance or radiating it as a far-field EM wave or recycling it through a capacitor. This resistance and/or capacitance can be outside or inside the PA.

In case of energy recycling through a capacitance, the capacitance then becomes the sink of energy and for the next quarter of the AC cycle - the source of energy for the coil.  And so, the energy sloshes back and forth between the capacitor and coil in the familiar parallel LC circuit manner.  When this "sloshing" is lossless then the PA does not need to replenish that AC energy, so the energy transfer between the PA and LC tank stops ...and the PA "sees" an open circuit. That apparent "open circuit" presents very poor match to the PA's output and this is what your SWR meter shows.

In realistic LC circuits, the energy "sloshing" between the coil and capacitance is being lost continuously in the resistance (as heat) and through EM radiation (because of radiation resistance), ultrasonics, ..and hopefully to proton's precession.  The PA must then replenish this lost energy.  The more needs to get replenished, the more energy flows form the PA to the LC circuit.  Eventually this reaches an equilibrium, where the PA supplies as much energy as is being lost.  Maximum energy transfer happens when the impedance of the PA is equal to the impedance of the load....albeit not the max efficiency. See: MPTP.

reading somewhat further back you say:
So does this mean that ONLY at the moment "the H-field generated between the coils does some work etc...." this will be seen as a dip in the reflection coefficient and SWR?
Yes, otherwise no energy will flow from the PA to the ideal parallel LC circuit.

However, realistic parallel LC circuits always have resistive and radiative losses and these will need to be replenished by the PA, causing some net energy transfer and dipping of the reflection coefficient and SWR.  My point here is that the maximization of the radiative losses (radio wave generation) is not synonymous with the maximization of near H-field amplitude because:
  • the radiative losses (generation of far-field EM waves) are proportional to the product of the radiation resistance and the square of the current amplitude.
  • the near H-field amplitude is proportional to the product of current amplitude and coil turns (ampturns),

The situation is a little different when the PA is connected in series with a series LC circuit, because then all the energy sloshing goes through the PA, so the PA's internal resistance and reactances participate in it.

If so, then there needs to be the focus on during the tuning i think.
Yes, the goal is still to obtain the maximum magnetic flux amplitude and that means the maximum ampturns.

If you think that your HF new magnetic field sensor is trustworthy (the one made out of the Litzed loop in the i-Probe), then this is the best indicator for tuning for the maximum amplitude of the magnetic flux.

* except you should have used the word "energy" instead of "power"
« Last Edit: 2020-07-12, 21:27:21 by verpies »
   

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I made some tests using the I-probe.
Seems the best pickup is with the curved loop parallel to the pancake coil windings.
Max signal in the middle of the 11 turns.
It looks like this magnetic probe is not sensitive only at its tip, bummer.  ..but it is still useful for relative peaking when tuning the trimmer.
Also, due to the nature of the magnetic coupling the angle of the Litz loop must influence its sensitivity in the given direction, so always rotate it in 3D to find the field's orientation.

I am not surprised that the SWR & Power meter readings do not correspond to the peak sensed by the magnetic probe, because not the entire current flowing into the pancake circuit is responsible for generating the desired H-field.  Some of this current flows between the coil's turns (via interwinding capacitance) and does not generate the H-field in the desired direction. 
This is why the magnetic field probe measuring method is superior - it ignores all the electronic parasitics!
   

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Oh no, no - don't you give up.

I did not say i give up, its just that my mind says that what i am trying is pointless, but i have tried pointless things many times before  :P

Ok,  i am starting to grasp it, thanks for your persistence.

Quote
* except you should have used the word "energy" instead of "power"

yes i knew that when i read it back, but i thought nobody will notice,       damn...

Itsu
   

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If you fall in love with you new HF magnetic probe and want to maximize its performance, then bring out your microscope and solder each individual strand of the Litz wire loop individually and varnish it so the solder joints do not touch.  Stagger the joints if you do not want a bulge.
I know, I know it's a lot of tedious work - but consider it a part of your test gear collection and that it does not need to be repeated.

Too bad, you cannot calibrate this new magnetic probe because you have no way of generating a constant amplitude H-field of varying frequency.
   

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It looks like this magnetic probe is not sensitive only at its tip, bummer.  ..but it is still useful for relative peaking when tuning the trimmer.
Also, due to the nature of the magnetic coupling the angle of the Litz loop must influence its sensitivity in the given direction.

I am not surprised that the SWR & Power meter readings do not correspond to the peak sensed by the magnetic probe, because not the entire current flowing into the pancake circuit is responsible for generating the desired H-field.  Some of this current flows between the coil's turns (via interwinding capacitance) and does not generate the H-field in the desired direction. 
This is why the magnetic field probe measuring method is superior - it ignores all the electronic parasitics!

Yes,  that relative peaking when tuning the trimmer is what i thought was the main purpose, this works nicely i think.



Still a question on my mind,   these 2 pancake coils are in series (bucking), but we have technically not a series capacitor, so does that make them a parallel LC circuit due to their interwinding (parallel) capacitance?

Itsu 

   

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Still a question on my mind,   these 2 pancake coils are in series (bucking), but we have technically not a series capacitor, so does that make them a parallel LC circuit due to their interwinding (parallel) capacitance?
I think so, but I am not completely sure.  It sometimes looks like a mixed series/parallel circuit.
I would like others to analyze this question too: Partzman, Smudge, Centralflow ?

Anyway, the H-field's direction between the pancake coils will be different than outside them.  Amplitude too, especially if they are not identical.
   

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If you fall in love with you new HF magnetic probe and want to maximize its performance, then bring out your microscope and solder each individual strand of the Litz wire loop individually and varnish it so the solder joints do not touch.  Stagger the joints if you do not want a bulge.
I know, I know it's a lot of tedious work - but consider it a part of your test gear collection and that it does not need to be repeated.

Too bad, you cannot calibrate this new magnetic probe because you have no way of generating a constant amplitude H-field of varying frequency.

Pfff,  you must be joking,  right?

Perhaps with the smaller litz wire coming, it has only 120 separate strands  :D
« Last Edit: 2020-07-13, 09:14:25 by Itsu »
   
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