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While we are on this thread and for what it's
worth.
I worked on a communication system that simply used an
audio amplifier driving a pair of electrodes in the water spaced about 1
meter apart. Electrodes were aluminum about 8 to 10 inches square 1/8 inch
thick. The receiver was simply another high gain audio amplifier. Also with
electrode spacing about 1 meter.
The transmitted power was 1 watt at an electrode impedance
of 1 ohm. The receiver was also matched for 1 ohm input impedance.
I made up a unit and listened to music while diving off
West Palm Beach.
This essentially has no transducers except for metal
electrodes. Very simple. The theory gives a fall off of the signal as a function
of 1/r^3 so it is short range, but still we were able to achieve 100 yards
range. For those versed in RF the propagation is near field in a conducting
medium. Maximum range is co-linear with the dipole not broadside.
The biggest problem with this link was it would pick up 60
Hertz and harmonics electrical noise. I found if you are in the Ocean
further than 200 yards the 60 Hertz pickup was minimal.
This is a very simple communication link and could be used
for sub to sub, sub to surface or sub to diver. Range would be limited to about
100 to 200 yards depending on the electrodes. One electrode could be the sub's
hull and the second a float or antenna.
This works since I have used it diver to diver. The main
problem diver to diver is it would require a full face mask so the diver can
articulate clearly. That's true of any diver communication.
Bear in mind the ultrasonic SSB has much, much greater
range.
Ken Martindale
----- Original Message -----
Sent: Saturday, November 15, 2008 12:12
PM
Subject: RE: [PSUBS-MAILIST] sound
transducers
Jay,
This is a very good point! I
think of a large amount of background noise in the case of a broadband system
would be like trying talk ten rows back in a crouded stadium during
a football game...It can be done, but it would not be easy at
all!
I am aware that much better systems do exist that filter
out most outside "extras" by using a very small bandwidth thru electronics
majic. These systems I'm sure are awesome and have incredible
range.
I am trying to help include those (such as myself) that
will delve into mainly shallower water (less than 200'), and are working
on a budget that won't budge. As I stated earlier, my goal is a modest
one...To clearly and reliably talk sub to sub while both are submerged at 150'
and both 150' apart...farther would be icing on the cake. I think this system
will work very well as both the transmit electronics and listen electronics
are exactly identical. (these input and outputs can also be switched in case
of emergencies also!) As best as I can tell, actual cb communications are
limited to a mere ten feet when done underwater! I am sure if we all work
together, we could do better than this.
The testing on this
most simplest of voice communications as I said is slated for Spring. We will
share all that we find both good and bad with the group at that time (If
nothing else, it gives us a topic to talk about) Thanks early for all the
support you
Guys!
David Bartsch
From: bottomgun@mindspring.com
To:
personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] sound
transducers
Date: Sat, 15 Nov 2008 09:45:14 -0500
David,
In open
water (salt) you are going to have varying irreproducible results due to
background noise (biologics + man-made), back scatter, reverberation,
temperature, and salinity issues. Most of these will degrade a given
signal and reduce dependability. Some days it might work and others it
might not. Freshwater is a more reasonable environment for your
endeavor. It is a complicated process to determine the maximum range
which will vary from place to place.
You need to
be careful with casual underwater comms as you may be happy with relatively
poor capability while chit-chatting but in an emergency, clear dependable
communications is mandatory to increase the probability of a successful
emergency resolution.
R/Jay
Jay K.
Jeffries
Andros Is.,
Bahamas
A skimmer
afloat is but a submarine, so poorly built it will not plunge…
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of David
Bartsch
Sent: Saturday, November 15, 2008 12:44 AM
To:
personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] sound
transducers
Jay,
What then would you think would be the maximum range of a broadband voice
system? Do you feel that 150' apart and both systems 150' deep is achievable?
Is fresh water the best medium for this system?
This was an attempt
to aid two submarines working together or perhaps talking to its support boat.
Do you think this goal is beyond reach with this set up? It was designed to be
as simple as possible to aid persons not rehersed in electronics to be able to
put these together with minimal assistance.
You stated that
salt water had odd effects on sonar reception as compared to fresh
water...this was shown at the convention with boats picked up much better in
salt water than in fresh. The acoustical pinger was masked by passing boat
traffic.
Please share what you
know...
David
Bartsch
From:
bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject:
RE: [PSUBS-MAILIST] sound transducers
Date: Fri, 14 Nov 2008 21:57:58
-0500
Joe,
For
efficient transmission, the signal is translated in frequency (still audible
but unintelligible) to maximize range and single side-band is used to conserve
energy.. Anything else will have difficulties of one form or
another. Opening a basic sonar acoustic text will document this, you
can’t get around basic physics.
R/Jay
Jay K.
Jeffries
Andros Is.,
Bahamas
A skimmer
afloat is but a submarine, so poorly built it will not plunge…
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Joseph
Perkel
Sent: Friday, November 14, 2008 4:55 PM
To:
personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] sound
transducers
David,
Not
having any field experiences and out of curiosity, this brings to mind a
question regarding underwater voice transmission in general.
I've
seen voice comm between Alvin and Atlantis, Calypso and the saucers,
habitats,..etc.
Is this voice comm severely scrambled (distorted
by the seawater), and then reprocessed by the receiving
equipment?
Or, put another way, if I swim between divers with
voice comm equipment, could I hear the conversation like I do prop
noises?
Joe
From:
dbartsch2236@hotmail.com
To: personal_submersibles@psubs.org
Subject:
[PSUBS-MAILIST] sound transducers
Date: Fri, 14 Nov 2008 15:36:04
-0500
To all:
The transducer
for solids from which can be made the broadband voice transmitters are
available on e-bay under "underwater speaker" at this time. These are selling
for $26.95 but shipping is being provided. This is not a bad price if you were
concidering delving into this area of study.
With a singing
machine that is battery operated, a voice transmitter can be made from the use
of this. (It still needs to be imbedded in molding plastic to survive deep
depths.) And you will still need a means of hearing the return
responce.
It sure would be great to talk back and forth
between two submerged submarines or to your support boat without having to
surface
first.
David Bartsch
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