TV antenna installation: How to ground
The main grounding electrode conductor (the wire running to the cold water pipe) is required to be terminated with a ground clamp. Wrapping it around the pipe is not a good connection. 

After fixing the ground clamp add an inter-system bonding block to the main ground wire (they sell these and the ground clamps at any big box store). It clamps onto the ground wire without cutting it. It will have a terminal strip for attaching the ground wires from your cable TV and the TV antenna. Attach those there. The cable TV isn't properly grounded either from what you said. 

The TV antenna ground wire can't be smaller than #14 AWG copper wire.

This all in addition to the ADU that Tester mentioned.