I am trying to control a RC submarine under 2 meters of clear water (or very slightly salted, much less than the sea). I would need to send about three servo channels at least four times per second, plus three binary channels (108 bps at the very least)
I tried a 2.4 GHz remote (http://www.banggood.com/FlySky-FS-i6-2_4G-6CH-AFHDS-RC-Transmitter-With-FS-iA6-Receiver-p-922606.html), like every newbie, and it failed miserably (maybe I should have researched a bit more before buying...)
The range is about 10cm underwater (I expected worse), then the signal drops.
I am now considering two other options :
Using a long antenna that reaches up to the surface (but I don't want to damage the nice antenna of the receiver, and I don't know if it will work)
Using a 433 MHz frequency (http://www.ebay.com/itm/271645282016). I know the smaller the frequency the better, but this is the lower I could find. I looked desperately for a 41 MHz transmitter but could never find the matching receiver, so I gave up.
I should receive it in about 10 days, I will keep you posted on how this performs.
I know the usual solution is hydrophones or lasers, but it seemed a bit overkill, and I don't have the time or the patience to build amplifying circuits, so I'll stick with the nice arduino modules if I can...
I also looked at AM transmitters, but again I couldn't find an appropriate receiver, and I'm not sure how to amplifiate the TX signal
Do you have experience in that domain ?