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Re: Wireless Transmission

Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx>


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, January 22, 2005 4:08 PM
Subject: Re: Wireless Transmission


> Original poster: robert heidlebaugh <rheidlebaugh@xxxxxxxxxxxxxx>
>
> Steve Conner. I liked what you said, but let me state a slight conflict.
> Ground waves do exist on the surface and within the earth. The phase of
> these waves differ from air waves by 90o That is a east west air antenna
> will propigate north south within the earth. It is common to beleave that
> radio waves only propigate within the earth at low frequency , below 65
Khz,
> but experiments prove 30 Mhz can be used to communicate within the earth.
>      Since we live on or above the surface very little research has been
done
> with sub-terra  wave propigation so little data is available on the
subject.
>         Robert   H

Getting a bit OT.. but
there's a lot of research on subsurface propagation, at all frequencies.
Low frequencies (<20kHz) are/were used for comms with submarines
Low frequencies are used in mines, caving, etc.
medium frequencies are used in geophysical prospecting
high frequencies (in the 3-30 MHz sense) don't propagate too well.
higher frequencies do, and are used in various and sundry sounders,
communications systems, orbiting and airborne imaging radar  (the latest fad
is looking for archaeological sites using UHF and L-band radars)

In any case, probably one of the leading theoretical researchers in this
sort of thing is J.R.Wait  --- search for "subsurface" and "wait" and you'll
get a host of references.