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Author Topic: Dally, Shark & Ruslan workbench  (Read 52069 times)

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Guess that that node should not be there.
Yes, the node at this place indicates wavelength to coil length mismatch....but maybe not to the coil+gizmo+antenna.


Also, the HF magnetic field sensor on the stick is great but the magnetic field is only one side of the coin in a TC/Kacher.

Consider adding an electric field sensor, too.  Like in this video:
https://youtu.be/U9yFrQ41Za0?t=69

This way you will have a dual-field (H&E) detector on a stick ...and you will be able to see much more.


P.S.
The H-field sensing coil can double as one side of the E-field sensor's pickup electrode....or they can be completely separate - whatever works best...

« Last Edit: 2021-08-02, 01:09:11 by verpies »
   

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OK,  is that a neon bulb on that stick, can't really see.

Itsu
   

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@ Vasik

Which grounding layout do you recommend for TCs ?

Blue is the primary. Green is a real secondary element. Gray is a virtual secondary element (image). The thick black line is the ground.
« Last Edit: 2021-08-02, 00:54:22 by verpies »
   

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OK,  is that a neon bulb on that stick, can't really see.
Yes, with its terminals spread like wings so they are immersed in the different electric potentials.
Copper or aluminum tape attached to these wings increases sensitivity (larger area, larger capacitance).
« Last Edit: 2021-08-03, 00:13:57 by verpies »
   

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@Nick, Itsu, Vasik, UtopiaNow, Szaxx

What is the VSWR of your TC/Kacher secondary ?

Quote from: the attached paper (pg.9, Ch.VI.B)
"The key performance parameter for high voltage Tesla coils is the VSWR on the resonant structure itself - the higher the better!"
   

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@ Vasik

Which grounding layout do you recommend for TCs ?

Blue is the primary. Green is a real secondary element. Gray is a virtual secondary element (image). The thick black line is the ground.

Verpies,

I don't really know. Do you think there is any significant difference ?
I think in Alexeev's and some Ruslan's videos we see option 4.

Vasik


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   

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I don't really know. Do you think there is any significant difference ?
In my experiments with TCs it made a difference.
Related: With dipole antennas the ground makes a small difference and with monopole antennas it is documented to make a huge difference.

I think in Alexeev's and some Ruslan's videos we see option 4.
The "TC Gnd 4" option is very sensitive to the length of the thick vertical black line segment on that diagram.
« Last Edit: 2021-08-02, 09:47:15 by verpies »
   

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verpies,

so the grounding layout (post #1702) would be the preferred one, so i will try to set up the kacher/antenna ONLY (remove the Grenade/inductor) this way.

Using a neon and some 2cm wires on both ends attached to a stick does show some activity, will use it to characterize the E-field in the new setup.

Thanks for the PDF's, will take a look and try to find out the VSWR of the kacher/antenna.

Itsu
   

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In my experiments with TCs it made a difference.
Related: With dipole antennas the ground makes a small difference and with monopole antennas it is documented to make a huge difference.
The "TC Gnd 4" option is very sensitive to the length of the thick vertical black line segment on that diagram.

Antenna theory is good, but we do not making antenna here, we don't want our system to radiate.
Comparing to wave length, height in our case is very small.

Vasik


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The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
   
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Hi All,
Watching the Russian videos specifically the TC/Katcher the earth wire should be as long as possible. This would become a mirror of the HV coil and if earthed into the ground via a rod the output of the whole assembly would be as close to a pure sine wave as possible. The pulses that feed the driver coil should be very short and the more the better. These also are required for the interaction to the grenade on a working unit. The gizmo needs to be close to the thick part of the grenade to permit the required phase shift and the feedback if set up correctly will phase lick the TC to where its required. The output transistor will do this too but the feedback the gizmo provides should keep the functional unit stable. The startup is where the unit suffers most and I've not found an answer to this so far.
You all can watch these videos with direct translation via Google translate if you can use a split screen approach on your phone or two screens which may prove difficult to view. Being nearly as old as some here and older than others I'm sure you can appreciate this eye bashing strain. On the app there's 3 options and I utilised the bottom right button which translates reasonably well with a bonus of the transcript being download able for anyone interested.
Itsu has posted previously about an interaction outside of what was expected and this may be the feedback manifesting itself on the scope trace.
   

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Antenna theory is good, but we do not making antenna here, we don't want our system to radiate.
I agree. Radiating antennas exhibit low VSWRs while TCs exhibit high VSWRs.
However, the grounding issues and the mirror images are similar.
« Last Edit: 2021-08-02, 22:33:14 by verpies »
   

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So i removed the Grenade L5 with inductor L4 from the circuit.
I rerouted the ground to be perpendicular to the bottom of the kacher and have only the kacher secondary bottom grounded, so like "TC Gnd 1" from verpies post #1702.

After firing up with the same configuration as yesterday (blue probe near by top secondary, purple probe at MOSFET driver input), the first thing to notice is we now do have the typical triangle shaped ringing signal being picked up, see screenshot.

We also notice we have about the same low voltages and power into the kacher as yesterday.

Probing the kacher with the double led/coil (H field) shows similar node / anti-node as yesterday and the new E-field probe only shows some activity across the secondary.

Video here:   https://youtu.be/jRIdTFwYDbM


I think i have to increase the duty cycle and/or the primary kacher voltage to be able to further investigate the shapes of the H and E fields.


I do have some other kachers / TC's which i can try instead of this present kacher to see if they perform different.


Itsu
   

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@Itsu

Do you have the driving pulses aligned to the self-oscillations of the secondary etc..., which I illustrated in this post ?

Probing the kacher with the double led/coil (H field) shows similar node / anti-node as yesterday and the new E-field probe only shows some activity across the secondary.
Yeah, when the frequency is tuned correctly, the highest E field reading should be at the "antenna coil".

Please take this diagram to heart when probing the E-field.  In your video, I have not seen the (b) position of the E-probe even once.

TC/Kacher Axial View.
   

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Well,  i did have (1.25Mhz), but probably the removal of the Grenade L5/Inductor L4 has some influence on the self-oscillation frequency of the secondary which i did not account for.

I will redo the test including the (b) position of the E-probe.

Itsu
   

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...but probably the removal of the Grenade L5/Inductor L4 has some influence on the self-oscillation frequency of the secondary...
I am sure it does.

Also the frequency characteristics and length of the gizmo makes the SRF incalculable. 
Empirically, at what driving pulse frequency do you obtain the maximum E-field on the "coiled antenna" when the gizmo is substituted with a piece of straight wire of the same length ?

I think that for these measurements you can avoid using the 1.2kV MOSFET if you drive it continuously (not only with 4 pulses) and 24V on the drain while the primary is narrow but large diameter (loosely coupled to the secondary).
You can always decrease the duty cycle of the driving burst (i.e. down to 4 pulses) later.
   
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   Itsu:
   If after removing L4 and L5 you still don't obtain the needed HV output, I would remove the "gizmo" and see if your output improves. As there seams to be no output even getting to the antenna coil. And it also seams like your gizmo is hogging up most of the weak Kacher HV pulses. Normally the gizmo improves the output at the antenna. If removing it does not help,  then it must be something going on with the Kacher circuit, itself.
   It also took me a while to figure out what was not right with my simple kacher.

   NickZ
   

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I was doing some testing, also using other tesla coils / kachers, but with the the low 4 pulses duty cycle, they had similar low outputs.

So i continued testing with a continue stream of pulses which does make the kachers more powerful.

I directly started to notice the effect of the RF in the room, like my DECT telephone starting to ring randomly and feedback into the 24V PS etc.

I was able to measure the self resonance of the Grenadeless kacher/ferrite/antenna to be 1.81Mhz, so quite a bit higher then the 1.25Mhz.

I will do some further testing like the ones mentioned above tomorrow.

Itsu
   

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Below are S21 VNA measurments of two "gizmos" (wide and narrow) wound on a 165mm x 10mm ferrite rod with a 2.5mm2 solid copper wire (5 CCW turns + 5 CW turns).
The windings of the wide "gizmo" are spaced 56mm apart, and the windings of the narrow "gizmo" are spaced 5mm apart.

For comparison I am also attaching measurements of a 10-turn regular helical coil wound with the same wire on the same ferrite rod.
   

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Looking great, thanks for doing that  O0

I am not that familiar with mU/ but i understand that 60 mU/ is the same as 6 Ohm/.

So for GIZMO_14 which is the closest to what i have presently, i see a dip around 4.2Mhz.


But at the frequency the Kacher/antenna operates (1.2Mhz) it will be way higher and presenting a blockage (GIZMO_5 comes closest).

I will try to take similar measurements of my gizmo.


Itsu
   

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I am not that familiar with mU/ but i understand that 60 mU/ is the same as 6 Ohm/.
That is: "Milli Unit per division".

Q: What is this "Unit" about ? 
A: It is a dimensionless ratio of 2 voltage amplitudes.  For example: 6V amplitude input into the DUT and 3V amplitude output out of the DUT would yield 500mU. In other word 50% amplitude attenuation.
If this were an amplifier, we would expect the measurements to be consistently above 1000mU (1U) ...indicating a net gain.

So for GIZMO_14 which is the closest to what i have presently, i see a dip around 4.2Mhz.
That is only for my ferrite rod.  Yours could be completely different.

The Imaginary part of the transmission through the DUT tells us about the phase delay that this DUT introduces.  Formally it is the amplitude of the 90º out-of-phase component of the received signal.

If you look at the green trace  (the linear magnitude of the transmittance) then you will see that at ~7MHz the total attenuation is 50% (500mU).  In other words: that "gizmo" acts as a Low Pass Filter.

I will try to take similar measurements of my gizmo.
If you do. Solder only the empty nuts which hold the SMA or BNC sockets to the copper plate and later screw the sockets into these nuts.  To raise the nuts above the surface of the copper plate (so the socket has a space to rotate) use a piece of a solder wick.

As ususal, don't solder when your RF cables are attached to the sockets. It ruins them.


« Last Edit: 2021-08-04, 15:12:34 by verpies »
   

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Hmmm,   ok,   so at ~7MHz the total attenuation is 50% (500mU) and at around 1.25MHz the attenuation would be 950mU, meaning 95% amplitude "gain" or in other words 5% attenuation?

Edit: changed to green line value at 1.25MHz to be around 950mU


Itsu
   

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Hmmm,   ok,   so at ~7MHz the total attenuation is 50% (500mU) and at around 1.25MHz the attenuation would be 950mU, meaning 95% amplitude "gain" or in other words 5% attenuation?
Yes
   

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Perhaps the purpose of the "gizmo" is to suppress the higher-order overtones whilst leaving the fundamental frequency substantially unchanged and consequently improve the spectral purity of the TC/Kacher oscillations according to the following principle:

Quote from: the attached paper (Pg.9, section 3)
During his investigation into ways by which standing waves could be suppressed on a λ/4 resonant structure, (Vitzmuller, 1987) investigated a helical coil of length H in which a length H1 was wound in the forward direction and a length H2 in the reverse direction. He established theoretically that the fundamental resonant frequency of the overall structure remained corresponding to λ/4 = H1+ H2, rather than to an increased frequency corresponding to λ/4 alone, a feature confirmed experimentally by the present authors. However, the frequencies and amplitudes of the higher-order modes are sensitive to the ratio H2/H1, providing a basis on which they can be controlled, whilst leaving those of the fundamental frequency substantially unchanged. It was this feature that was utilized to improve the spectral purity control of the output from a Tesla transformer.

In other words, the "gizmo" might leave the amplitude of the fundamental self-oscillation frequency almost unaffected and attenuate the higher overtones.
« Last Edit: 2021-08-04, 16:24:55 by verpies »
   
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Hi All,
What would be an interesting experiment with the gizmo would be to pulse a magnetic field at the node frequency and measure any output from the gizmo coil combination. It is known that the ferrite should be for low frequency use as found in mains filters. I assume this may lower the nodal frequency more towards the 1. 2MHZ we are using.

From the Russian videos, the early transistor kacher circuit where the low side of the HV coil is connected to the base enables a free running oscillator that is influenced by local environmental fields. The few short pulses fed to the base will sustain the ringing requirements for synchronisation permitting the feedback to change the phase to what's required. They also mentioned that the antenna/loading capacitor should be wound the opposite way to the kachers HV coil. This coil needs to be a different metal too, aluminium being mentioned as the effect is very difficult to obtain if using a copper coil.
I hope this info is useful and will aid us in obtaining a working unit.
   

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What would be an interesting experiment with the gizmo would be to pulse a magnetic field at the node frequency and measure any output from the gizmo coil combination.
I do not understand.
What is "node frequency" ?
What is "gizmo coil combination" ? Does the "coil" in that phrase belong to the "gizmo" or are are you referring to another "coil" which is external to the "gizmo" ?
   
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