Re: Extra coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Fergerson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mfergerson1-at-home-dot-com>

Tesla list wrote:
> 
> Original poster: "Nebojsa Kovacevic by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <morfeus-at-EUnet.yu>
> 
> Hello Mark!
> 
> Very good explanation. Tesla discovered that a long coil of wire behaves as
> a sort of "electromagnetic
> organ pipe". Some people think that this is important for creating an
> "invisible wall" using TC. The
> prediction is:  if we "modulate the field harmonics" a bit so that the
> voltage maximum does NOT appear
> at the end of the coil, but instead appears a few inches away...

  Then we (you, Antonio [if you're reading this], and I) agree
that you were suggesting the "extra coil" is modellable as a
generic resonator, and might be replaced with a microwave cavity
to be (inefficiently, I suspect) shock-excited by an "ordinary"
TC?

  As I mentioned, I'm interested in the limits of TCs, including
the possibility of a microwave version.

  Now I'm wondering about the coupling method. With a typical
hollow, metallic cavity, capacitive seems out because of the
likelyhood of arc-over, unless the cavity be very large. Magnetic
seems unlikely for the same reason, unless the input and output
"loop" be large. What's left? A dielectric resonator? AIUI they
can be coupled in and out by "evanescent waves" merely using
nearby conductors. I'm referring to a vague memory of  an article
I read that described DROs (Dielectric Resonant Oscillators)
built for several GHz using little discs of synthetic sapphire (I
think) and stripline coupling circuitry. But I don't know much
about how to determine impedance and Q for DRs.

  Even without output coupling circuitry, it sure wouldn't look
like an ordinary Maggie, with streamers coming off the end of a
chunk of an obvious insulator!

  As to your latter speculation, how do you force a voltage
antinode _off_ the physical coil? ISTM that at resonance you
_must_ have an antinode on at least one end of a nxlambda/2
(where n is odd) long resonator, and a node on the other end.
Even if you're running off-resonance, a node can appear off the
end of the coil, not an antinode.

  OTOH Antonio, if you're reading this, and the above is actually
possible, am I right in intuiting it could be part of the cause
of racing sparks? Since no TC system really operates at one
frequency, but at two or more, whose separation is determined
(largely) by the coupling, perhaps the one which is "shorter"
than the length of the coil can somehow "yank" the antinode off
the bottom of a, say, improperly RF-grounded secondary? Or will
any interference be more likely manifested at the topload?

  Mark L. Fergerson