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Re: Extra coil



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 All!
> 
> Thank you all for the comments about the extra coil. I was considering that
> coil strictly from the
> theoretical point of view, don`t have any experiences with coils like that,
> only with 'regular' ones. But
> I would like to know from all of you who had the practical experiences with
> extra coils, what are the
> diferences, comparing the three system with two system coil? Is there any
> dieference, and is it really
> irrelevant?

  Not from direct experience (yet; I'm still in the process of
trying to build possibly the smallest magnifier setup ever), but
some thoughts about "theoretical" viewpoints:

  A crystal radio is a CW device, which means its internal
currents and voltages are more or less steady state.

  A TC is an impulse device, more like a set of coupled bells or
tuning forks. That may seem to be a difference without a
distinction, but if you look at the transfer of energy between a
pair of bells or tunung forks _during the period of transfer_,
you see an increase in energy in one at the expense of the other.
The frequencies and amplitudes of oscillation are not steady
state.

  Both systems are modeled with the same sets of equations, but
with different limits. I suppose you could compare a magnifier to
a set of three bells/tuning forks, in which you pump energy into
the first, and get it out of the third _before you put any energy
into the first again_.

  There's filtering going on in both systems, but to different
purposes. In the CR case, the incoming frequency isn't what's
wanted, it's the modulation envelope's frequency. The incoming
frequency's energy is "sacrificed" continuously (to get the
modulation frequency's energy to a usable level), so the
resonator's characteristics are optimized to block one in such a
fashion that it's rectified, and pass the rectified voltage which
gives the modulation envelope. In the TC, the incoming (primary
resonant) frequency is what's wanted, just at larger amplitude,
so we change the characteristics of the following resonators to
give larger amplitude without affecting the frequency
(hopefully). The only "modulation" occuring is the time rate of
energy transfer, or "bang rate".

  Having said that, I'm starting to wonder about SS or VT TCs
with their "weird" modes of operation, frinst staccato mode, in
which it seems that other frequencies are added to (or rather
modulated onto) the resonator frequency to get those strange
spark shapes.

  Also, I think the OP's reference to "microwave ovens" was a
mistype; could he have meant "microwave cavities" as in
considering the extra coil to be a generic resonator, and
replacing it with a cavity to be excited with the output of a
standard TC? ISTM that it's possible, if not likely to be
especially effective.

  I've always wondered how to build a microwave TC...

  Mark L. Fergerson