Re: SSTC As a transmitter.

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



> If you're not using EM radiation, you don't need the license. You
> just need to convince the inspector that you're using a non-EM
> radiation :)
> 
> During the '70s some radio amateurs were keen on what they called
> 'earth mode' communications, which basically involved pumping lots
> of LF power circa 20kHz into the ground, using two electrodes set
> into the ground quite some distance apart.  The receiver uses
> a similar pair of electrodes to pickup up the differential voltage
> due to the current field in the earth excited by the transmitter.
> As you can imagine the signal strength falls off very rapidly with
> range.

And essentially, this is how the big ELF comm systems work... Once it's
propagating, the loss isn't too bad, but the antenna efficiency is horrid,
even with a 5 mile x 5 mile grid as an antenna/transducer.

> 
> And what is meant by a 'slow-wave' resonator?  Does the adjective
> mean anything?

Some structure along which a wave propagates at less than free space.  Good
example is a distributed LC delay line or the structure in a TWT, where the
wave propagates at the speed of the electrons going down the center.  The
Corums used the terminology when describing their (now deprecated) theories
of TC function (basically a 1/4 wave transmission line much shorter than
free space 1/4 wave because propagation is in a "slow wave structure")..
Terry's measurements of voltage and current phase at top and bottom of
secondary, and your modeling work, have pretty much shot that theory down.

> 
> > The lowfers use a technique called coherent CW which I think
> > uses WWV to synchronize transmitters and receivers.
> 
> Yes, WWV, and in UK, the MSF, can be used to sync both the
> carrier frequencies and modulation phase at each end.  Extremely
> narrow bandwidths can be used to enhance signal/noise ratio, and
> the limitation here tends to be phase distortion during
> propagation, which sets a limit to the minimum reciever bandwidth
> in any given situation.

Similar schemes are used in EME communications, or any very narrow band,
low data rate application.  Personally, I think that phase modulation is a
pretty horrid way to transmit data through a dispersive medium.

> 
> On the whole, a non self-oscillating CW TC should make quite a
> good exciter for a short (wrt wavelength) wire antenna.  The
> high impedance at the top of the coil is appropriate for the
> high radiation resistance of the short wire.  A low frequency
> antenna tuner correctly set up to match a transmitter into a
> short wire would look a lot like a base-fed TC.

And, in fact, a former co-worker of mine (an active Lowfer) basically built
a big litz wire secondary to drive his antenna.  Around a hundred turns on
the secondary (using plastic trash cans as the forms).  There are (were?)
some funky rules about antenna size (max tophat, max height, etc.). And,
yes, if you disconnected the antenna, you could get some mighty fine sparks
off the top of the secondary.

Another good practical example is the networks used to drive the antennas
for Omega.  Anyone contemplating working on sending power/information (same
thing really) with low frequencies from tesla coils would do well to study
up on Omega and Loran.  There's quite a bit on the web about them.