Long Range Wireless Computer

[zboss]

Hi Folks,

Having crazy thoughts on election day. More just curiosity than anything... I am wondering if there is some scientific limit to the range that wireless transmitters for dive computers can achieve? The reason I wonder:

I was thinking that it might be useful if a dive master/instructor could have a dive computer that receives all of his students/paying guests vital information? This way he could monitor depth and air pressure for everyone in his group and if one of them goes out of sorts the computer could sound a warning.

Even more so... the dive boat could have a receiver to simultaneously gather the data. Or the transmitters could also act as repeaters and triangulation devices.

What do you think or am I just feeling "gadety" today?

 

[maractwin]

Broadcasting with enough power to cover distance underwater would mean short battery life, and so much power that when turned on above water, (at least in the U.S.) the FCC would probably want it licensed. And you'd have to do something fancy to avoid having the transmitters interfere with each other.

And is it really a good idea? A good instructor/guide should keep visual contact with his charges, as there are many ways to get in trouble that the computer wouldn't notice. If a dive boat wants to log that info, it's easier to download it to a PC after the dive than collect it during.

-Mark

 

[Austin]

Still, that's an awsome idea! True they should be keeping track anyways, but it would be great instead of stopping, asking a group of ten to show fingers for how much psi, having someone say that they have more than they do so the group doesn't have to turn around, then, 5 minutes later, 200 yards from the boat someone comes finning up to the Divemaster showing him his guage that reads 500psi. That's always fun, think if that could be avoided!

 

[donacheson]

Still, that's an awsome idea! True they should be keeping track anyways, but it would be great instead of stopping, asking a group of ten to show fingers for how much psi, having someone say that they have more than they do so the group doesn't have to turn around, then, 5 minutes later, 200 yards from the boat someone comes finning up to the Divemaster showing him his guage that reads 500psi. That's always fun, think if that could be avoided!

And just think! Divemasters could pony up another $1K or more for every "receiver" they had to carry to accomodate all the different brands of hoseless dive computers their customers might own. <G>

 

[herman]

It would not be too big of a feat. You should be able to use VLF (very low frequencies) RF which penetrates fairly well in water. Data rates would not have to be too high and battery life could be extended by updating the data at intervals instead of using real time. Given the limited range necessary, I would think a hundred yards would do, the power requirements could be kept to a minimum. FCC licenses would not be much of a problem, there already is an experimenters band in the VLF range that unlicensed radios can operate at with out FCC aproval. It's been a long time since I played with VLF but seems like the max power was around 1.5 watts, that should be plenty, esp if an UW recieving antenna was used for on boat operations. Getting the cost of the equipment down to a reasonable level would be the biggest challange.

 

[zboss]

And just think! Divemasters could pony up another $1K or more for every "receiver" they had to carry to accomodate all the different brands of hoseless dive computers their customers might own. <G>

manufacturers could including these transmiters internally to the first stage, kind of like what oceanic is doing with their heads-up mask computer.

The advice on the transmission power is more along the line of what I was looking for. My physics question for the day is: why can't the kinetic energy from the air released by the tank be used to drive the power supply?