Underwater Data Link?
 

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

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" wrote in message
. ..
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

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)

Next one is a laser diode connection to some modem. I note that in the
cell phone world one can connect a laser/optical fibre device direct to
the RF output stage of the TX. This may sound far fetched but I wonder
about using a laser diode and phototransistor connected to an ethernet
switch. I have NOT thought this through at all so pls done burn me too hard!

I think the data rate of using an acoustic path would be way too low.
You have to allow for major multipath reflections through the medium and
I see this as bringing it down dramatically. There are probably some
signal recovery techniques that can be used in this situation but I dont
know of them. Personally I'd like to fiddle with Wyman/RDFT encoding in
a voice bandwidth and see if that works. It has adjustable forward error
correction which might just make it do-able. You tend to need a PC at
each end though!

Apologies for the waffling

Cheers Bob Vk2YQA

Eric wrote:
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.)

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.

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?

Eric wrote:

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

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

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

Eric wrote:
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.



Thanks!

Cheers
Eric

Probably more than $500 but worth a look

http://www.link-quest.com/html/models1.htm

Dennis

Thus spake nitespark :



Bob Bob wrote:
Its all intriguing anyway! Not that I have a large enough body of water
nearby to try experimenting with it though.



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?

I have family in Tyler. It was a "non event" there, according to my
bro. Further east it turned to ****. Imagine being evacuated from NO
to Houston to Texarkana. Talk about being **** upon.


73
Andy
--
dillon

Pain is Nature's way of saying "that was stupid"