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Dave,
This would be interesting to look at.
The main question I have is how do we test
it?
I have some of the set up now. I have a receiver set up
with a low impedance input (around 1 ohm) with a 18 watt amplifier so
that's one end.
I'll look around and see if I can get a second set
up.
Ken Martindale
----- Original Message -----
Sent: Saturday, November 15, 2008 4:09
PM
Subject: RE: [PSUBS-MAILIST] sound
transducers
Ken,
This system could really find a use
with subs! Any chance you could make a setup again? The more options available
to us, the better as some may prefer this over
acoustics.
David
Bartsch
From: wmartindale@cfl.rr.com
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] sound
transducers
Date: Sat, 15 Nov 2008 13:36:04 -0500
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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