Re: Goubou line, "G-line" (was Tesla Coil RF Transmitter)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Bill,

On 13 Sep 2005, at 22:30, Tesla list wrote:

> Original poster: William Beaty <billb@xxxxxxxxxx>
>
> On Sun, 11 Sep 2005, Tesla list wrote:
>
>  > Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>  >
>  > 3 -- given the above statements, why is it so hard for anyone to >
>  believe that Tesla was transmitting by conduction through the earth,
>  > and not propagation through the air?! Just becuase you CAN transmit
>  > RF through the air, doesn't mean it is the ONLY way to do it."
>
> This isn't quite correct.  RF energy cannot flow through conductors.
> After all, whenever we send electrical energy down a piece of coax or
> a length of lampcord, both the coax and the lampcord function as
> waveguides, and the electromagnetic energy is flowing through the
> space outside the metal and not flowing inside the conductors.  The
> current is in the metal, yet the flowing energy is in the space
> nearby.
>
> If Tesla successfully used the Earth to transmit VLF energy from place
> to place, the energy had to have flowed through the air, not through
> the Earth.  Yes, the EM energy was associated with electric currents
> in the Earth's surface.  And the EM energy would be constrained to
> follow the Earth's surface.  But electrical energy doesn't move
> through conductors. Look at microwave waveguides (the hollow
> rectangular type), where the currents are in the metal surface, while
> the RF energy is in the hollow center of the pipe.  Coax and twinlead
> are similar, and they still behave as waveguides regardlesss of
> frequency.
>
> Or in other words, *ALL* electrical energy is the same thing as "radio
> waves."  Electrical technology is all based on propagating EM fields
> guided by electric circuits.  The only difference is in our minds:
> when electromagnetism is guided by some wires, we concentrate on the
> currents in the wires, ignore the surrounding field, and we call it
> "electrical energy." But when it flys off an antenna and crosses empty
> space, we call it "radio waves."  Yet the energy is made of
> space-filling EM fields in either case.  Similarly, the only
> difference between a power supply and a radio transmitter is...  the
> radio transmitter is connected to an antenna. So Tesla's system was
> using the Earth as a waveguide in somewhat the same way that the
> electric utility companies use copper wire as waveguides.
>
>
> Here's where it gets weird.  Perhaps Tesla's system did not actually
> take advantage of the Ionosphere at all.  After all, in the microwave
> waveguide system called the "Goubou Line" or "G-line," there is an
> electric current in a single conductor, and the EM waves are guided by
> that conductor.  A "G-line" system is fed by conventional coax cable,
> but then the coax shield is flared out into a horn shape called the
> Launcher, and the center conductor continues on alone.  At the far end
> is another "horn," the Catcher, which leads to the shield of normal
> coax.  In between the horns the single wire has no return path, just
> as there is no return path in optical fibers or in rectangular
> microwave waveguides.  Or, from an e-field standpoint, the single wire
> functions as it's own return path, since the fast-moving regions of
> positive and negative charge on the long "G-line" wire are connected
> together by electric field lines.
>
> An analogy:  if electric circuits are like drive belts wrapped around
> pulleys, then Tesla's system was sending sound waves along a single
> length of stretched rope.  When frequency is high, no closed circuit
> or return rope is neeed.
>
> If Tesla's system is similar to microwave G-line, then the Earth's
> ionosphere plays a less significant role, since the single conductor
> itself is the only necessary part.  But in that case, the "launching
> horn" is the important part.  The smaller the horn, the worse the
> impedance match, and the harder it becomes to send electrical energy
> along the single wire.
>
>
> Hmmm, I wonder what happens if we actually try sending signals along a
> couple hundred feel of coax cable, but we strip off the shield braid
> in a fifty-foot length in the middle of the cable?  Well, I guess it
> would only be a fair test if we used 100MHz signals or higher, so 50ft
> is many wavelengths long.  Also use ungrounded signal generator and
> detector, so there's no earth-return path.  Could we light a light
> bulb over such a transmission line?  (Of course put a tank circuit on
> the light bulb to take advantage of resonant matching effects.)

I would argue that a single wire is really just the "centre" conductor
of a two wire transmission line with the "outer" conductor (if one wants
to liken it to coax) having a rather large radius. I don't see any
way of avoiding some coupling to the surroundings, relatively distant
though they may be.

?
Malcolm


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