Underwater Data Link?

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E-mail me and I'll hook you up with an old swabbie I know who can probably
build exactly what you need.

I also know that some line of sight devices have been made using blue-green
lasers, that allow P3 Orion aircraft to communicate discretely with US subs.


"Eric" <none@nospam.not> wrote in message
news:GtXYe.50848$vJ4.22348@tornado.ohiordc.rr.com...
> Hi,
>
> Don't want to get side-threaded, but I got hit up on a project idea that
> should prove practical, educational, fun, and just plain neat.
>
> What will be required, however, is a wireless data pipe down to a depth of
> ~50 feet (15m). Unfortunetly, it will have to be wireless.
>
> (Obviously, such a link will also have to be acoustic and not RF.)
>
> I can't go outside of "consumer" price tags though. By "consumer", I'm
> thinking up to ~$500.
>
> Depth time on a full battery charge of at least 30 mins is prefered.
>
> Standard data ports, such as ethernet or RS-232.
>
> I'm not concerned about the data rate through the water, or what
> mechanism/schemes these modems use going through the water (proprietary,
I'd
> imagine), as long as the data ports use standard communications.
>
> If the modems behave and function (from their physical ports, not
> modem-modem through the water) as a standard "analog modem", I plan on
using
> just a terminal program with the surface modem. Port speed should be a
> non-issue, as long as its standard. Even just 300 bps will work fine.
>
> If the modems behave and function (port side, again) as standard "network
> cards", then I'll be doing TCP/IP. Again, only need the bare minimum data
> rate for function.
>
> It would be nice if such modem could function like both above, giving more
> flexibility, but I can do with either.
>
> Its not going to be passing graphics, images, or anything extensive
through
> the water. In fact, the relevant data it will be passing will only be 15
to
> 20 characters in length.
>
> I "thought" that I had seen such an (consumer) animal in the past years
ago,
> and mentally noting that it "neat", but I may be mistaken. My googles
are
> only turning up such modems that are either commercial or military,
> obviously outside my reach.
>
> Just throwing this out in hopes that maybe someone has seen such an animal
> with a consumer price tag -- or possibily an idea or two on how to maybe
> creatively homebrew such hardware, relatively inexpensively, out of
existing
> hardware. If need be, I can kludge up power supplies and waterproof
casings
> (able to withstand 15m) for anything creative...
>
> Thanks!
>
> Cheers
> Eric
>
>

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Bob Bob wrote:
> Hi Eric
>
> First thought is that I have read somewhere about underwater antennas.

At one Computex (Taipei) I attended, there was a company showing an
Ethernet hub that worked under water. This was a wired network.

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Bob Bob wrote:
> Hi Eric
>
> First thought is that I have read somewhere about underwater antennas.
> They were a lot shorter than what you have in air and the attenuation
> was much worse. Might be worth some research. If you (say) ran a couple
> of hundred kilohertz you could FSK or PSK that at some low data rate.
> Perhaps even drive it with one of the older 1200/75/300 modem chips. (ie
> RS232 serial data) I mean this is how the US subs get their action
> messages (although this is a really low data rate)

> Apologies for the waffling
>
> Cheers Bob Vk2YQA
>

Bob,
I suspect if he wants to go wireless, he is going to have to go further
down the RF Spectrum than a couple of hundred khz, even for that short a
distance. The OTS comm systems for their full face masks have a range
just slightly over what he desires, operate around 30 khz SSB. At that
frequency, he is not going to be able to move a great deal of data very
fast but as I recall, that was not a factor. I use an Aladin AirZ
hoseless computer and I think the transmitter operates around that same
frequency range.

Nice to see folks from "VK" land here with us.

73 OM
Andy
WD4KDN

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Bob Bob wrote:
> Its all intriguing anyway! Not that I have a large enough body of water
> nearby to try experimenting with it though.
>
> I did a quick bit of browsing around and even found some experiments
> done by a VK5 using 160M (http://www.qsl.net/vk5br/UwaterComms.htm) I
> note he has some attenuation curves that might be worth a look at.
> Although some kind of packet, PSK or other kind of digital system would
> work in an SSB bandwidth the problem for the OP is that he probably
> doesnt want to take a PC with him underwater! Still think a packet TNC
> at 300BPS might be usable though.
>
> I am actually here in more ways than one.. Am living in East Texas.
>
> Cheers Bob W5/VK2YQA
>
> nitespark wrote:
> ---
>
>>
>> Nice to see folks from "VK" land here with us.
>>
>> 73 OM
>> Andy
>> WD4KDN

I agree Bob. Quite interesting. I was diving last weekend in a quarry
with two other divers who had wireless comm systems using full face
masks. I could hear them talking to each other but couldn't make out
what they were saying. They have been trying to talk me into purchasing
a full face mask with comm but at present, I have other financial
priorities. I guess for a very limited distance, 160 meters might work
but depending on the application, battery size and the associated tx
power would be limiting factors. The article mentioned floating an
antenna to the surface. If you were to do that, you might as well use
VHF or UHF depending on distances and power outputs, etc. For most
divers, I would think that would not be their first choice because of
entanglement issues.

If you are in East Texas, depending on where, you are getting pounded by
"Rita". Hope all goes well. Perhaps we can hook up on 20meter?

73
Andy

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"Bob Bob" wrote in message..
> Also this
>
> http://www.grantsystems.com/pdf/beeman.pdf
>
> Looks like a system at 150Mhz.
>
> Maybe use a 2M txcvr, a shortened antenna and a packet TNC! Lots of
> these can be bought second hand very cheaply.
>
> I assume you are licensed to use amateur equipment?

Hi,

(This is reply to both of your messages, along with a reply to others in
this thread as well.)

Apologies for not getting back to this thread until now. I had something
come up that kept me busy all weekend, and it looks like it will continue to
do so until early next week.

I did read all the replies though and all were very helpful. That link you
gave for the PDF will be very helpful as well. I've only had time to
briefly skim over it, but look forward to reading it in detail as I'm not
familiar with propagation through water at all.

The laser idea is pretty cool. (Wonder if IR would work at all, have to
look that up later.) From googling, found some other folks that put
together some homebrew robotic projects and had various levels of success
using DTMF. They were using generators/decoders just for simple commands,
but got an idea in my head brewing on how to turn sequences into characters
(with even some rudimentary CRC), and not requiring any computer coding at
all.

As for a license, unfornutely I don't have one (yet). I do have experience
with commercial and military communications though (mainly SHF, tactical and
fixed SATCOM, LOS/Troposcatter microwave, etc) on both the radio side
(converters, synths, amps, filters, antennas, ect) and data side (muxes,
modems, ect). Planning, when time avails, to go to a local ham radio
meeting and getting involved with the hobby.

Cheers!
-Eric