Underwater wireless video

No, water is a conductor !

Dave

The "big boys" use fiber optics. Jim Cameron's ROV's are all wired like that, for instance.

Just as an FYI. Designing for underwarer is infinitely more difficult thatn designing for outer space. Do your math.

Brian

reseach ability of RF to xmit through water at the freq of the units you're looking at.

VLF works (but check the baud rate) research land base to submarine communications

if you're planning a wired ROV ignore wireless, simply add 2-3 conductors to the unit. Most cams require power / ground / video out though I have used a DC block and shared the power conductor with video out.

if you're thinking an untethered ROV (AUV) ... research underwater modems (acoustic) they'll handle video but not the frame rate one associates with realtime (25-30fps)

if your rov is shallow depth .. tow a buoy / marker that is also an antenna feed to the unit ... that could work

- Ed

got talc ? Drysuit talc & bags

I know it would take a lot of power, but what about free-space optical? Avoid red because of absorption IIRC, a while back there was an idea to replace VLF comms to subs with satellite-based green lasers.

FYI standard PPM remote control signals can penetrate water a meter or two and are used on RC subs (of the model variety). Although the depths Brian is interested in RF would be unsuitable.

If the ROV is tethered then an RF signal could be transmitted up the umbilical cord (preferable to a digital signal perhaps), perhaps even through the power cables, although noise would be something that would have to be taken care of.

Tim

...and the antenna size.

Thanks for the advice folks. There are wireless underwater video products out there, but at a cost much higher than my price range for this project (just doin' this for fun).

Since it will be wired for control reasons, I might as well just use a wired camera. Much cheaper I'm sure too.

Thanks!

Brian

Excellent point. The wavelength alone for VLF is 10km - 100km. Assuming you use a 1/4 wave antenna, it's still prohibitively huge. ELF also works, but the antenna size is even bigger (100km - 1000km)

---The Mad Jesuit

No. The standard (legal) video transmitters operate in the 2.4GHz band. This happens to be very near, if not at, the peak absorbtion frequency of water. If you put the antenna on a surface float it will work, but not very far underwater (1-2 inches), if at all.

Tim