Terry Spragg wrote:
A single hyrophone cannot tune out interference from any
[lots of good stuff snipped]

Thanks for your comments.
I may try the frequency shifting and filtering idea.

[previous note on electronic detectors...]

Derek,

Haven't found the thread from years ago, but this is an example of the
basic circuit that might serve as a "ship detector". The second link is
a source page with other links of possible electronic interest.

http://www.techlib.com/electronics/lightning.html
http://www.links999.net/security/det.../detector.html

Rufus

[previous note on electronic detectors...]

Derek,

Haven't found the thread from years ago, but this is an example of the
basic circuit that might serve as a "ship detector". The second link is
a source page with other links of possible electronic interest.

http://www.techlib.com/electronics/lightning.html
http://www.links999.net/security/det.../detector.html

Rufus