Tesla spoke of the need for a solid earth ground base. Colorado Springs and I believe Long Island are both granite.  This might provide a clue,  might the energy transmitting frequency be very low?  Also he spoke of nodes in certain part on the globe.  This implies very long wavelength

a little clarification video

https://youtu.be/U6XVGYu1oF0

As I tested L4 resonance I have connected it from inside rim of L3 to outside rim of L4.

But now I will connect inside rim of L3 to inside rim of L4. with outside rim of L4 connected to the large grounding cap C4.
(I will need to rename it to stay consistent with the circuit part names).

So reverse connected. the series resonant voltage of L4 should be inphase with the parallel resonant voltage of L3.

the question is, should I flip L4 over and make it counter rotating relative to L3?

because the impulse should excite the system.

I wanted to use logic to get it right. but in my experience I have had it wrong so often, that I now choose to simply experiment and see what works and what doesn't.

but what is an indication that it works? how can I see if L4 is series resonant with C3?
I guess, this will be clear due to the extreme high voltage magnitude. So... hmm better hook up a load. to keep it down?

ok, I added 3uF to L4, and reverse connected it in series to L3
So L3 inside rim, connected to L4 inside rim.
L4 outside rim to 3uF cap, and cap to ground.

When L4 is flipped over it dampenes the L3 sine wave amplitude.  So I will leave it rotating the same direction as L1 L2 and L3.
L4 series resonace should add up to L3 parallel resonance.

L1 impulse should be tuned, to L4 coil resonance (no tuning cap). but how do I measure that? By disconnecting L4 from the L3, and see what frequency it has (while coupled to L3).

Then L2 L3 should be tuned to a sub frequency of L4

orange show L4 resonance by itself (close coupled to L3, L4 had 3uF to ground on outside rim)
L3 tuned with 21nF, L2 with 51nF
F=126.46kc/s

L4=605 kc/s
1/2 period= 1654/2= 826ns this should be the length of the impulse

impulse is now 392ns
I should add capacity parallel to L1 to get around 826ns (prefer to be slightly less)
This will take away from the voltage of the impulse, but I can tune to a lower harmonic of L4.
base frequency of L4: 605
1st sub 302.5
3nd      201.5
4rd       151.1
5th        120.9
6th       100.8
86.35  kc/s this is the 7th subharmonic of L4. and should be able to still get a proper impulse voltage.
8th       75.6 kc/s
9th       67.2kc/s

9x68pF in parallel with L1 makes the impulse 669.6ns at 86.35kc/s using the large 20m L4 coil. I will use the smaller l4 coil witch is better matched for L1 .

getting around -1700V impulse at full power 0.83A 2x 32.3V  adding more capacity to L1 would reduce the impulse voltage further

Im still having doubts if I should tune the impulse to L3 or L4
since the L2 L3 act as capacitor plates, where the impulse sets up the displacement current. So if L3 is the plate that feels it, shouldnt the impulse be tuned to L3???
Or is the L4 feeling it also... I can see it ringing so, it must be pretty good

I series connected L4 to L3 which detuned it a bit, so I tuned again (by frequency, so its not the ideal sub harmonic)
and measured L3 current (green)
input power: 1.36A 2x 32.3V DC
f= 87.1kc/s
same L1 L2 and L3 caps as before
26.6A !!!  peak to peak on L3

I never had it this high before. thats insane :shocked:.

 So the theory seems to work. L4 series resonance, is added up to the L3 parallel resonance.
 :clap2:

now to tune it perfectly...

cant measure L4 voltage as its equal to L3
but I can measure L4 current vs L3 to see if its properly resonant

L4 current is much weaker than the L3 current, and is 180 degrees out of phase right now.
with current probe arrow always pointing inwards.

I will now replace the large L4 coil, with the smaller L4 coil, to better match the impulse speed to the L4 speed

smaller sized L4 (equal dimensions with L3 inside and outside diameter, but 0.75mm2 wire,
does not show the ripples of its own resonant frequency, I will need to detune L3 again, to get less current, so L4 can be free resonating
L3 was 41nF L2 111nf

I tried several L2 L3 cap variations to get the L4 ripple clearly visible, while coupled to L3.
L4 is outside rim connected to 3uf to ground.
While inside rim is loose, and probed.
It copies the L3 voltage sine wave, and barely shows its ripple.
But with L3 and L2 caps maxed out (117 and 61nf) I could barely see a ripple on L4,
I zoomed in and measured around 1428ns for 2 periods.
so devided by 4 gives a half wave of around 357ns
This is good, as the impulse now is almost matched without a c1 capacitor parallel to L1, being around 397ns

ok, subharmonics of the impulse. I used the impulse half wave as I had it already tuned to L4 in previous experiments, so since I can measure it more precise I will use it as a reference. But only as a rough guide line, tuning still needs to be played with.

impulse half wave give a frequency of 1257kc/s (397ns)
5th =251
7th=179
9th=139
11th=114
13th=96.7kc/s

scr70 show L4 current in green, around 4A pp
scr69 shows L3 current in green around 15App
L3 L4 current are out of phase
this is at f=96.7kc/s with L3=32nF and L2 =117nF
power 0.92A 2x31.7V =58.3W
impulse is around -2500V

I wonder what happens when I place L4 in between L2 and L3 to receive the impulse directly, but then I need different coils, as it is impossible due to the epoxy.
instead, I will tune the impulse to L3, and see how that works

L4 current being out of phase with L3 current, would suggest, that the current flows from L3 into C3 while L4 current flows form C3 into L4, and vice versa, so opposite flows. That is not what it should be, both should feed in and out of C3 simultaneously. so they will add up.
Now L4 is being fed by L3, instead of feeding L3?

still it can be seen that the impulse is feeding both coils, as they appear to jump up in current after the impulse, but how can that be?
Is one half of the impulse feeding, L3 with the other half of the impulse is feeing L4? as an impulse is a double polarity displacement?

maybe, I need to use an equal size L4 (to L3) so the impulse feeds both equally.
but then there is no increased inductance in L4, which whould amplify. but I might needs to let go of that brain fart.

oR... load it, and see what happens now?

I will remove the L3 connection from the L4 and C3.
so i can see if I can make L4 series resonant with C3, and look at the phase of it.
if it doesn't work, I'll make L3 series resonant, amd see if that works, if so, L4 will be made parallel resonant

yes, L4 becomes series resonant, and is tunable. this was at 95.63kc/s with L3 detached from c3 c4 (open ended, but coupled and grounded)

secondary L3 is now parallel resonant, L4 extra (will be) series resonant
but... would it be the same with L3 series resonant and L4 parallel resonant?

It seems that the primary needs to be series resonant due to its low impedance, which makes it able to pass the high voltage impulse through it. So in a sense, parallel resonance, with its high impedance, doesn't let energy pass through it.

At the same time, the L2 primary impulse sets up a displacement current. Which flows through the dielectric medium (epoxy/air/earth) thus, it flows through, materials of HIGH impedance. so called, isolators/resistors.

Thus the displacement current, would love the L3 parallel resonant coil, as it has high impedance, just like the epoxy has high impedance. That would mean that it flows throught L3 (which also acts as a capacitor plate) towards L4. Since L4 (will become) series resonant, it has low impedance. thus acts as a true coil (low resistance) where the displacement current is transformed into conventional current? or at least it is stopped, as the displacement does not conduct through low impedance.

still I see both L3 and L4 amplified in current, while their phases are 180 degrees opposite...
hmm...

Time to flip L4 around

ok, L4 is now flipped over, which means it is counterrotating vs L3.
before, the flow was cancelled out, but not now! maybe due to using the other coil.
without retuning, Im still using 11nF and at 92.3kc/s as before,
I now see that I am around 3 octaves below resonance. (3 periods per impulse).
and low and behold. current of L3 and L4 are now in phase. as accepted. but this does not mean L4 now is charging the cap at the same time, as the rotational direction has changed.
So.. lets tune this.

I gave L3 (and l4) the max amount of capacity, 61nF and this made it possible to tune the system to 125kc/s
current in L4 is still fairly low. (L3 current in green with scope shot)
But its good to see that there now is no cancelation. So I will stay working with L4 flipped over right now.
L4 coil has its series bridge wires, on the wrong side, so I will need to reconnect it so that it can become close coupled to L3 again.

I don't believe L4 is series resonant yet, I might need to try different kinds of capacitor sizes.
Will looking for a sudden jump in voltage (current phase shifting?) when L4 becomes reosnant

since L4 is now feeding of L3 parallel resonance, it makes sense that when L4 does become resonant, the current phase will flip, as it starts feeding into L3. And thus produceing high voltages and currents. (what... even higher? yes! we need a load when this happens, or turn it off instantly.)

I will reverse L4 again, so it is rotating the same direction as L3 again, and put a load over it, then retune, for max output power

I need to remove L4 and
test L3 parallel VS series resonance. see if the frequency changes with the same tuning capacity

L2 primary has large capacity so when resonant it has relative large current and low voltage sine waves.

the impulse stands out on L2 due to it's relative high voltage.

When looking at the current we should be able to see the sine wave jump from zero up, at the time of the impulse, this should represent the ideal displacement current. lets look for that also.

the newest tesla coil designs which show the straight white discharges seem to do the same, a ramped current flow.
I believe steve ward designed this.

https://youtu.be/A3dwgdpA7WM

https://youtu.be/dazlMI30XP0

I tested L3 in series mode and parallel mode, which gave the same results, same frequency 110.2 kc/s
same voltage current and power input.
scr74=parallel
scr75=series