Bandwidth over 300m tether?

I’m working on an ROV targeting a max depth of 300 meters. I need at least two 720p30 video feed, but three would be better, as would higher resolutions.

My original plan was to use HomePlug, but from what I’ve read it seems the bandwidth drops quite a bit over that much tether.

Does anyone have experience transmitting a few tens of megabits over this much tether? Recommendations on how to do it over a single twisted pair?

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There have been several threads over on the Blue Robotics Forum concerning the performance of long tethers. I suggest that you check there.


300 m video feed using copper wire… is that possible ? I would guess that we are talking about fiber ???

Unless something has changed, I’m pretty sure fiber doesn’t use twisted pairs.

I’ll check over at BlueROV, thanks.

Max distance for CAT5 is 100 m, after that the signal will be unstable. Sending video signal down 300 m cable i would guess you will have a lot of signal loss. Maybe there is somekind of signal booster, or not to use cable but change to fiber.


Check out this Blue Robotics tether interface board as it has a video amp on it for improved video signal transmission. Only drawback is that is it 480 composite only.


most of ROVs nowadays can only go around 100m with tether?? i recently search some, there’s one can go deep like 150m,but most ROVs go like 100m right…but it really depends on what you are looking for…300m sounds really crazy …with a tether>??..nah…

That interface board looks like it would be a good last resort option. I could run the ROV on a single 480p feed, but it wouldn’t be ideal.

Thanks again everyone for the input. Currently investigating using a fancier tether that incorporates a fiber optic cable, or just adding a second fiber tether to a Fathom tether. Probably it’ll be the 480p composite to start, and upgrade to fiber down the road.

FYI, this is for a lionfish hunting ROV. Unlikely to ever go below 200m (and mostly much shallower than that), but I’m trying to design for a bit of headroom just in case.

If you are actually diving 300m deep in open water you will need a lot more than 300m of tether. 1000m is a good estimate of the actual tether you will need if there is any significant water current.

Current is pretty much nil where I’m planning to operate. 200 meters is the deepest I expect to ever want to go, mostly it’ll be 20-50 meters.