Re Longituidinal Waves

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

> Original poster: "David Thomson by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

> Hi Dave P.

> I put together a page this morning that will help you to visualize
> what is happening and why longitudinal waves are real.

> http://www.tesla-coil-builder-dot-com/solenoid_coil_dynamics.htm
 
> There is no doubt at all that longitudinal waves exist on the ground
> plane.

        I remain unconvinced.  As to 'buried coils', be aware that
        ground screens, roughly 1/4 wave long, up to 120 or so,
        are routinely used for AM Broadcast.  Have been for near
        100 years.  (these 'simulate' a buried 1/4 wave.  All standard
        radio.  At higher freqs, the ground plane shows up as three
        or four radials.  OR a half wave element is used. cf any
        antenna text.
 
> I would venture further and say that radio waves cannot be detected
> along the ground (or at least they will be severely diminished.)

        Take a radio, any freq, place on ground and let us know.
        (hint: commonly reception improves.)
 
> How many HAM operators do you see trying to receive HF with antennas
> lying on the ground?

        Those without trees?  Those with hurricanes?

        Different freqs involve different techniques.  (actually:
        the same techniques, they IMPLEMENTATION looks different.
        Borrowing the 'cup' analogy:

                A canteen may not look like a wine glass, each work
                alike.

        Typically HAMs operate at above 2MHz and up.  underground
        antennas are commonly used at 200KHz and down.  
> Yet, even though there are no radio waves along the ground,

        cf above.  There are plenty.

> there are longitudinal waves.  And these waves are much more
> concentrated in energy than the voltage wave counterparts being
> radiated into space and underground.

        perhaps.  Conventional RF is strong in 'near field', roughly,
        the inner 1/4 wave, if i recall.

        (one wonders why most longitudinal wave research is
        with Tesla coils at low freqs.  One Assumes such waves
        ought to exist (....) at all freqs, and other freqs and
        sources are easier to work with...

> >       There is a whole class of nearground and underground antennas,
>>        for specialized applications in electromagnetic and radio
>>        work.

> Can you give some references?

        Obscure subject, granted.
        Doubt if available off amazon-dot-com.

                ELF Communications Antennas, Burrows.
                        Several chapters.

                Antennas in Inhomogeneous Media, Galejs
                        Several Chapters.

        I seem to recall seeing one called, simply:

                Underground Antennas

        Didn't buy it so dunno the author.

        best
         dwp

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