How does power up the coax? Is power really travelling up the coax or is there a power line bundled with the RG-59? Does it have an impact on the video signal?

A: Power is travelling up the coax. A blocking capacitor is used in series with the video to handle the DC power component, while a filter capacitor is used to filter video out of the AC signal. Remember that with power up the coax, it’s always DC.

Cables like this are specifically designed to function within their build parameters and that means the internal power signal won’t trouble the internal video on their shared path. The EMI danger will be external mains, plant rooms or electric motors.