Homebuilt ROVs Forum

Hi guys,

I was wondering if it would be a good idea to transmit digital signal through the tether using FSK modulation. This would allow fewer distortions and reflections in the wire. And in consequence this should allow further distances

There are some cool modules that can already make the modulated signal. Then to demodulate the signal I should only make a low pass or high pass filter before putting the input in an microcontroller.

What do you guys think?

here are some pictures showing FSK modualtion:

A good idea. Not one I've ever seen used in the industry, but I can't think why not. I'd be interested to see how well this works.

Just made some first tests. It looks promising.

Big plus for you is that in water sound travels further. Disadvantage of this system is that you only can do half duplex and think about both the land side and rov side sending information at the same time which generates more noise.

fryslan76 wrote:Big plus for you is that in water sound travels further. Disadvantage of this system is that you only can do half duplex and think about both the land side and rov side sending information at the same time which generates more noise.

It can also be Full duplex. I use one frequency for the controller and another frequency for the submarine (two different ultrasonic sounds). They shouldn't create problems. I would use filters in both ends to ensure I only receive the frequency I want.

Nice trick, did not thought of that one