>Just to throw in another possibility, there is a small window in the IR
>spectrum that will transmit well through water.  But please note that VLF
>is the best way to go in water.  The scroedinger wave equation can show
>that any EM wave's propagation is a function of medium density and wave
>frequency.
>
>                                                        - Dennis
Hi Dennis,

I think you are confusing density with the electromagnetic
properties of the material. And further confusing propagation
velocity with absorbtion.

The electromagnetic properties of the material determine the
absorbtion (attenuation).

In the case of microwave absorbtion, the absorbtion spectrum
relates more to the molecular structure.

Back to VLF, there is a VLF transmitter in Australia at
Exmouth Gulf on the West Coast which transmits to the Indian
Ocean. I think the frequency is just a few Khz. In any case
the antenna is over 1000 ft high! This system is used to
communicate with US submarines. I don't know if they
trnasmit video though. :-)


Ray Gardiner (DSP Systems) ray@dsp-systems.com http://www.dsp-systems.com
private email to:- ray@netspace.net.au