From my experiences, not much. I've seen a small flicker when my mux was activated, but aside from that, not a whole lot of jitter. Depending of definition, you might want to just leech off your motor supply lines instead.
Alternately, make sure your Signal Ground and Signal Supply are on the same twisted pair.
Camera questions?
Re: Camera questions?
you will get a better signal if you use one pair of cat 5 twisted wire (2 conductors) and a pair of video baluns. One at at the camera, and one at the surface.
Re: Camera questions?
This is Paul again... just wanted to mention that I too like others am shooting for at least 300 foot tether, but the max depth of the lake that I am wanting to explore is 663 ft when completely flooded...US Army Corps of Engineers. I think that my actual design other than thrusters will handle this depth I am working on redesigning the thruster to handle at least a 1000 feet. Right now i just need about 200 feet. As I said before I am working on a small... very small deep deep sea submersible mostly for observation that is extremely low cost to the operator. Like to try to keep it under 3 grand if poss... not really out for the money...lol... but would be nice 
Re: Camera questions?
oops did I say that my thruster could handle 1000 feet... oops didn't mean that they are only bilge pump motors,.. but would like them to be able to handle that at that size.