I have a blue tooth queston .

[starcrafttom]

I was wandering how far a bluetooth signal would travel under water? I have a use in mind and was wandering if this is the technology to use or not. Any experts in the field out there?

 

[Sneaks]

Forget it. Bluetooth runs at 2.4 Gigahertz and I seriously doubt the power levels used would get you more than an inch or two under water.

Don

 

[tom&shan]

Not really sure about underwater -
from bluetooth.com
Range
The operating range depends on the device class:
Class 3 radios – have a range of up to 1 meter or 3 feet
Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 30 feet
Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet

 

[rogerbum]

Bluetooth only travels about 30 ft out of water and operates at a frequency of 2.4GHz (low frequency microwaves - almost exactly the same frequency as most microwave ovens). Given the frequency, the range in water will likely be less than a cm at most. Water absorbs most microwave frequencies quite well (which is why microwave ovens work as well as they do). Salt water will be more absorbent than regular water. The only radio waves which travel effectively through salt water are very low frequency (or extremely low frequency) radio signals such as are used for communication with submarines. So, if you want to get a signal to something below water, wires are the best option.

 

[Captains Cat]

Plus, if you have blue teeth, the water is probably too cold!! :shock:

Charlie

 

[starcrafttom]

well the class 1 with 300ft would be what I want but if it will not travel under water then it may not be a choose. I have done some looking around on the web and one guy used a blue tooth device in water at one foot and that worked ok. the reason I ask is that using wire is the limiting factor to my evil plan. too much drag and to hard to handle two cables at once.

 

[rogerbum]

Two things-
1) For the guy who used blue tooth under water and got a distance of 1', was he in salt water?

2) Drag can be lessened by making the cable thinner. For many applications where there isn't much current being carried, the cable thickness is limited by the necessary strength of the cable. Depending on the specific application, it may be possible to go with really thin cable.

 

[starcrafttom]

roger, there is a system out there with a cable that acts both downrigger and video. its made by walker downriggers and seems to be a good product. but what Iam looking for is a system that can be used and moved from one boat to another. that can be used on a pole or a line without the downrigger and for that mission It has to be wireless. if that can be built and cost kept under a thousand bucks then I could sale that system all day long. The camera exist as well as the viewer so I dont need to re-invent the wheel but going wireless would open so mnay uses for a camera while fishing both in and out of the water.

 

[rogerbum]

If you want a real-time display, I think you're going to be stuck with a cable although it would conceivably be possible to send some video images back through water with high frequency sonar signals or even with laser transmission, that would require some serious engineering. However, if you would be happy with video that was recorded to a small tape or hard drive from a small self powered unit, that would be easily doable at low cost. You'd have to pull it up to see what it saw but you would get rid of the need for cables.