Re: Hydrophone

[Pet Porpoise Pool <porpoise@midcoast.com.au>]

At 01:27 AM 2/15/99 -0500, you wrote:
>Hi, Scott:
>        When you say 'hydrophone', do you mean an actual hydrophone used to
>receive ambient sound (water column noise, crustaceans, whales, etc.) or to
>transmit into the water on a broad frequency range - such as communicating
>with divers without receiving equipment . . .or do you mean a wireless u/w
>sub to surface unit operating on a specific frequency???
>
>Phil Nuytten
>
>Further to this I am currently experimenting with a video transmiter
attached to a small ccd camera which we are attaching to seals and dolphins
in captivity with the intention of following and monitoring whale movements
but are having trouble with the signal reception when the animal is
underwater.
I am not in the least technical in mind or skill but understand that in
order to stop refraction of the signal caused by the water( or actually the
change in density)  you would have to use a very low frequency carrier
signal in order to transmit under the ocean this is backed by the fact the
USA use ELF (Extremly Low Frequency) ground based areals that are over 50
miles long to communicate with their nuclear sub fleet, I believe they have
only recently( past 5-10 years) been able to actually recieve signals from
the subs while submerged.
The point being if anyone out there has ideas or practical solutions to my
problem I would love to hear from you.

Hope that all made sense


Troy