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RE: [PSUBS-MAILIST] system completetion
Alec,
No such luck with the marine VHF...underwater SSB comm is done at ultrasonic frequencies...on the order of 20-30Khz. A marine VHF (which is Frequency Modulated as opposed to Single Side Band) operates at a frequency in the neighborhood of 156 Mhz. Way too high a frequency...the water would absorb all the RF energy within a couple of feet. We do know that sound travels well underwater though. While David's system will work in relatively quiet conditions, if you get in a crowded lake or river with a lot of motor boat traffic or general U/W noise, it will be a different story. Probably more like trying to whisper to someone across a crowded room at a party. That's where ultrasonic comm is a better choice (albeit more expensive). You are still working with sound but it is outside the audible range so you can filter out all the audible noise, demodulate the signal, and have clear audio. Now it's far from perfect....it is still line of sight (get behind a shipwreck and no comm) and is affected by thermalclines, etc.
I have a design for a VLF SSB transceiver that could be constructed for less than the comercial (OTS, etc) units, although I haven't done a detailed price estimate yet. The biggest hurdle is finding a reasonably priced, commercially available transducer to use (which is why I enquired about your Divelink transducers). Commercial ones are in the $100's or even $1000's of dollar range and the only affordable ones are replacement ones for OTS and others who appear reluctant to sell them separately unless you can prove you already own one of their units.
I can publish the schematic for those interested and possibly even get some PC boards made up (after redesigning the output stage to drive a transducer instead of an antenna) but the last time I offered or inquired, nobody seemed interested. It all hinges on finding an affordable transducer that I can get electrical specs on.
Al
----- Original Message -----
From: Alec Smyth <Alec.Smyth@compuware.com>
To: personal submersibles <personal_submersibles@psubs.org>
Sent: Tue, 19 May 2009 14:04:19 +0000 (UTC)
Subject: RE: [PSUBS-MAILIST] system completetion
Thanks David, I'm really interested but will wait to see what Divelink
come back with before making a final decision. It's fantastic you're
doing this, I appreciate it. While a single sideband unit from OTS is
probably the ultimate, I really like something that we can build
ourselves and 350' sounds like sufficient for most PSUBS operations.
Basic question... I have a marine VHF sitting on a shelf. Is it possible
to leverage that so that underwater it would transmit/receive through a
hydrophone instead of the antenna? Sorry if this is a completely
ignorant question, but it's just provoked by the fact it already has a
handset, speaker, and amplifier. I'm envisioning the addition of a
switch between surfaced mode (antenna) and submerged (hydrophone), but
imagine it couldn't be that simple. This is something I really know
nothing about.
thanks,
Alec
________________________________
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of David
Bartsch
Sent: Tuesday, May 19, 2009 02:06
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] system completetion
Alec,
Dean just received his console #4 and has placed a request for yet
another unit. Seems he wants one for his support craft as well.
Les already has two units and posted some test results from earlier
this year. He cut holes in the ice on a nearby pond and was able to
cross talk some 350' apart.
The system I have developed is a basic communications system that uses
an underwater speaker and the listening device is our HBH-2 hydrophones.
Two boats simply talk back and forth. There is no carrier so as ambient
noises rise, the range will diminish.
I looked into "underwater speakers" and actually bought one only to
find the maximum operating depth was but 14'. (This would have been real
useful to us) I have discovered that by installing a sound device for
solids into a metal dish and pouring two part molding plastic, you can
make an underwater speaker capable of going down quite deep. (exactly
how deep is yet to be established) This special transmitter is not
expensive and can be seen under special projects under my name and "UW
COMMS".
The cost for a complete system including two passive hydrophones and
this voice transmitter is $245.00 and in most instances, this includes
shipping.
A cb styled handset automatically shifts the unit from receive to
transmit and back again once the message is sent.
The basic block diagram is on the last picture under UW COMMS and I
will aid anyone who wishes to make a unit of like construction on their
own. The preamplifiers and amplifier cards are kits from various
suppliers that anyone with a little time and patience can put together.
The battery is self supplied and is 12 vdc. (this negates the need to
ship lead)
The goal was to make available a simple to use underwater
communications set that will allow two submarines to talk to each other
while both are up to 500' down and 500' apart. Talking from sub to
support vessel without surfacing would also be nice.
Dean has yet to try out his latest toy, but from those that have
ventured into the world of underwater sound with these things, I have no
complaints.
At present, console #1 is with Frank D. in California, #2 and #3 are
with Les Katschor in Michigan, #4 and soon #5 will be with Dean Ackman,
and more will follow.
These are easy to build, repair and maintain and should make submarine
activity safer as these consoles allow for the listening of ambient
noise such as boat traffic.
The newest attempt at a sonar system is essentially only a single
amplification channel for listening only. This should be great for
collision avoidance.
If you think you would enjoy a simpler form of communications with
in-club support, just give me the word.
David Bartsch
________________________________
Subject: RE: [PSUBS-MAILIST] system completetion
Date: Mon, 18 May 2009 13:34:08 -0400
From: Alec.Smyth@compuware.com
To: personal_submersibles@psubs.org
Hi David,
I'm getting my sub ready for the summer and one repair item was the
Divelink comms. One of the units failed and I just posted it to the
manufacturer who will test and provide an estimate for repair. They may
come back with some silly number. So I was wondering what the latest is
on your version? Did Dean get to test this?
thanks,
Alec
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From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of David
Bartsch
Sent: Sunday, May 10, 2009 02:17
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] system completetion
Dean,
Your passive sonar/underwater communications console #4 is completed
and has passed all of the initial in-lab performance testing.
This electronic enclosure along with its two passive hydrophones
(HBH-2) and single broadband voice transmitter will be shipped out to
you on Monday, May 11th via U.S. Postal Priority mail. A simplified set
of laminated operating instructions will also be provided.
I am pleased with this systems performance as I am sure you will be
also...good luck with your submarines launch and call should you have
any questions.
David Bartsch
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Al Secor
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