Tether waterproofing/depth/length constraints

[Keaton Hare]

Hi all, it seems like the accepted tether method is Cat5e, what are the general max length/depth restrictions for ethernet tethered ROV operation? I'd also love to see how y'all implemented tethers on your project, as well as the specific cables you used. I'm attempting a relatively deep-diving ROV and I am interested in using ethernet or other cost-effective cable as deep as it can go, and perhaps below that reverting to AUV operation, as it seems an off-the shelf tether of that length is extraordinarily expensive

[pabbott]

Depends on what you are calling deep diving. My ROV has a tether length of 200m. Anything over 100m is reaching the limit of reasonable responsiveness to topside commands and video latency. The simplest solution if you're not an electronics nut, is to just buy the Fathom X from Bluerobotics.

Also highly recommend using dedicated neutral buoyancy ROV tether cable if going below 100m.

[Oddmar]

You can go 4000 ft. over RG59 coax if you use two ethernet-over-coax adapters, one in the ROV, one topside. I used a security-system DVR inside my ROV plugged into a wired router, so I could also have 8 camera feeds.