Re: Hydrophone

[Phil Nuytten <72020.572@compuserve.com>]

Soory for the late response re 'Hydrophone' . .I was in Los Angeles over
the past few days . . Gee, "any info on surface/sub communication' is a
huge subject! Typically, submersibles stick to 'UQC' - type ( low)
frequencies (10 khz) or 'high ' ( about 27-30). Low freqs are best for
range (this is the standard used by many military subs) while 27- 30 is
shorter range, but much higher intelligibility. These systems are expensive
to buy, but very simple to build - (at least a functional version !) The
best units are the result of much tweaking and filtering. The digital
revolution has made even relatively low cost SCUBA communicators as good as
yesterday's best submersible units - so that's a good place to start! Stay
with single- sideband carriers rather than AM  systems for best
intelligibilty and range. 
        Sorry to be so short, but this is the subject for a tech paper!!
Oh, yeah, if you want near-perfect comms and dont mind a light umbilical to
the surface ( not attached to a vessel) go with a surface bouy ( the heavy
plastic inflatable type - 'Scotchman") and run your VHS up to an antenna 
on the bouy and then communicate via hand held or console mount VHS in the
sub. The tether can be very light so it doesn't much impede your speed - we
use  0.134 nylon-jacketed kevlar . . .it has a breaking strain of  at least
2500 lbs, so you can haul up the sub (!) or, at least, use it as a
messenger line to send down a self-socketing lift line  ( see " Submarine
Escape Systems - OTC paper, Houston, 1973 by  P. Nuytten) for details.
Jeez! That was 26 years ago!!!
Regards,
Phil Nuytten