Re: Radios, Sonar Communications, (Response to Charlie)

[protek@shreve.net]

Phil,
    I feel dumb asking this question.  But, when you describe these
communication systems at 10KHz and 30+KHz, are you talking about actual
radio transmissions or acoustic (sonar) transmissions?  I never thought of
SSB as a mode for underwater communications, but it does allow for more
power in the intelligence signal and not so much waisted power in the
carrier, as opposed to straight AM.  If you were talking about radio
propagation, it might be interesting to try applying SSB also to acoustic
transmission.  The filtering for such would be easy using DSP techniques.
    Of course my sub does not go anywhere as deep as those you have
developed.  If I did use say a 2 or 10 meter radio off the shelf, do you
have any idea roughly how deep this would go in fresh or salt water.  I
have no earthly idea.  I do know that I have talked in fresh water from
about 20 feet deep on 2-meters with a handheld actually inside the sub just
propagating through the viewports.
    There is another questions I would like to ask you.  I have had a
constant headache trying to make reasonably sized water-tight electrical
connections to withstand say 100 PSI.  Things wind up being large O-ring
sealed housings having the actual standard coax or power connections
inside.  The wires must be potted into the housing or sealed with a
water-tight fitting of some sort.  Are their any reasonably priced
connectors, that are easy to come by, that solve this problem?  A subbing
friend in Texas used a standard AMP Series 1 or Series 2 (can't remember
now) connector which has a small O-ring for his thru-hull connections, but
this scares me somewhat.  This connector was never designed for such
service but has worked for over a hundred dives as deep as 100 feet.
    I appreciate your info on the communications approach.  It has me
thinking.

Gary Boucher



At 12:06 AM 8/2/99 -0400, you wrote:
>Gary - try Single Sideband . . .10 KHZ for longest range ( but lowest
>intelligibilty) 30+ KHZ for medium range, high  resolution. AM systems are
>simpler and cheaper but don't come close to SSB. We have tried SCUBA
>communications, but they just dont have the oomph to punch through the
>ocean thermoclines or provide long range. A good SSB system, between 10 -
>20 watts , should give you clear comms at one mile range( in good
>sea/ambient noise conditions). There are a number of systems on the market,
>currently. 
>
>Regards
>Phil Nuytten 
>
>