F6, was I correct in assuming that you haven't yet explored the experiments and reference materials you asked me for?
I have experimented with Tesla coil couplings. It is all conventional, I have not found any anomalies, nor do I see any in past experiments by others. They confuse the effects either with near field coupling for short distance links or with electromagnetic waves for long distance links.
So I am waiting for convincing results from other experimenters, which is why I was interested in your US/UK transmission, which might well demonstrate this if it succeeds.
I asked you how you would eliminate the likely artifact of an electromagnetic wave, since this is the huge weakness of long distance experiments with Tesla coils, and I don't see any commitment on this point.
I asked you where you were with your project: no answer.
Instead I see the usual rhetoric about theories that are unfounded because they are not proven by experiment, often off topic (e.g. the question of transmission lines), those created by this mythology around Tesla. I am not part of this bigotry, sorry.
If you say you are experimenting, please really do it, tell us where you are at, and provide your concrete results, even if they are negative because we learn from them too.
As far as I'm concerned, and until I get proof of the contrary from those who believe in it, there are no longitudinal waves produced by Tesla's coils. And the little that could be produced indirectly would anyway be completely masked by the EM waves generated by the current in the coil, a coil that is a classical radio antenna and that Tesla's experimenters do not even bother to screen!
I do not deny the possibility of the existence of a longitudinal wave in free space or others, but it will be complex to implement, the level attenuating in 1/r² and not 1/r like an EM wave.
I have already provided links to a much better formalization of the longitudinal wave theory, such as that of Zaimidoroga recently mentioned by Grumpy, who also proposed with Podgainy an extension of Maxwell's equations to include the longitudinal wave ("Nonrelativistic theory of electroscalar field"). There are others, like B Zohuri who arrives at results similar to Zaimidoroga, or Zhakatayev. As for the experiments, there are many of them, in particular linked to the scalar wave itself linked to the potential vector, some of which I have tested, such as that of Zimmerman with plasmas. It is also confronted with the possible pollution by an electromagnetic wave (my duplication of this experiment was inconclusive because of that) but also because the experiment, as for Tesla's coils, can be explained classically (see the conclusion of the reproduction that KJ6VW made).
One must understand that the existence of a longitudinal wave imposes the loss of gauge invariance, which seriously challenges a solid part of physics. The potentials would no longer be relative but absolute.
So before tinkering, we must put everything in perspective to understand what we are dealing with, to avoid doing anything and drawing conclusions that are as false as they are hasty on what we observe in the experiments.