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From: jerry@oliveb.UUCP (Jerry Aguirre)
Newsgroups: net.physics
Subject: Re: passing  water
Message-ID: <170@oliveb.UUCP>
Date: Fri, 14-Sep-84 20:35:07 EDT
Article-I.D.: oliveb.170
Posted: Fri Sep 14 20:35:07 1984
Date-Received: Tue, 25-Sep-84 02:28:56 EDT
References: <13195@sri-arpa.UUCP>
Organization: Olivetti ATC, Cupertino, Ca
Lines: 55

I don't remember all the details but I did one read an article about
a way of transmitting signals thru water.  The diagram was something
like this:

				------
			       |      |
			       | XMTR |
	 ----------------------|      |--------------------------
	|			------                           |
	|			                                 |
////////|////////////////////////////////////////////////////////|////
	|			                                 |
     -------			                              -------
    |       |                                                |       |
    | Metal |                     Water                      | Metal |
    | Plate |                                                | Plate |
    |       |                                                |       |
     -------			                              -------


			    ----	  ----
			   |    |  ----  |    |
			   |    |-|RCVR|-|    |
			   |    |  ----  |    |
			    ----	  ----

Transmission range is restricted to the general area between the
two plates.  Go to deep or to far off to the side and you lose the
signal.  Still, plates on either end of a lake or section of river
would give you total coverage of the area.  The transmission should
be low frequency, probably in the 1 to 500 Khz. range.

I don't think the effect can properly be considered radio.  I think that
it depends on the conductivity of the water to transmit the signal.  The
receiver just intercepts the current flowing thru the water.  This
results in the signal only being available between the tranmission
plates.

For your application this would still require long wires to reach both
ends of the lake but does result in a "free" probe.  It does not address
the problem of how to get pictures back from the probe.  I think that if
it was possible to have a wireless underwater probe then someone would
have done it.  As other netr's have pointed out there is a lot of effort
going into communicating with underwater subs and drone probes of the
type you suggest.  Every one I have heard of either used a tether (fiber
optic is the latest) or took photographs for later recovery.

It is probably possible to sent pictures via sonar but not very quickly.
Ham radio operators send slow-scan pictures but at 14 seconds a frame
you might have trouble dodging the cliffs.

Ah, if someone would only invent a nutrino transmitter and receiver.

					    Jerry Aguirre
{hplabs|fortune|idi|ihnp4|ios|tolerant|allegra|tymix}!oliveb!jerry