Ken,
The only actual transmission test performed thus far, has been with the use of but a single fully functional two amplifier channel passive sonar/underwater communications console now in the hands of Les Katchor in Michigan. This unit being only the second such produced unit made use of a toggle switch to change from the upper channel (passive hydrophone for listening with its internally installed speaker)) to the lower channel (the microphone voice transmission and with this transducer for solids underwater speaker). This was needed so as to protect the listen electronics from being damaged from an overload condition. (I may be being overly cautious as the installed chips will cut off amplification to avoid this condition)
Using a small set of jumpers and with the transmit levels set to minimum output, I bypassed this safety feature and was able to transmit with this lower channel and with headphones listen with the upper channel at the same time. I used an above ground 18' in diameter pool with the voice transmitter on one side and the passive hydrophone placed on the opposite side.
As you can imagine, the transmission was very loud and very clear. I would have loved to have tried this in open water, but having but a single functioning console then in my hands, this was not possible.
In that both the transmit and recieve circuits were identical, I am confident the results would have been impressive.
Good luck and be sure to share with us that which you discover...
A simple pretest would be to connect this transmitter to the output of standard stereo just as you would a speaker...It will not seem loud but you will not be able to feel any vibrations such either as you would from a standard air operated speaker...This just indicates how well the coupling will be with the medium of water. below the waterline it will really impress you.
One more tech tip...Install the transmitter in the jaws of a vice (use the installed mounting bolts to secure this) the next time you make one...this aids in getting rid of extra heat (a crude heat sink) caused by the chemical reactions during molded plastic as it cures. I did this during the last one and the plastic did not shrink away from the metal dish as it cooled as before. (this really does not effect the unit as to how it performs though, it just looks better) And do not touch this pan during curing...It will bring a whole new meaning to phrase "give me some skin".
David Bartsch
From: wmartindale@cfl.rr.com
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] sound transducers
Date: Sun, 16 Nov 2008 15:01:30 -0500
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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