RJPNJ,
Article 810-21 gives your answer, congrats, that's one of the most missed of the grounding spots.
It allows you to go to your water pipe, but the best (lowest impedance) would be directly to the service ground. The code also requires this to be as straight as possible, also for impedant reasons.
Not a good idea to drive a separate ground rod, if you do, you have to run a #6 to the system ground to be legal anyway, otherwise, a # 10 will do.
Is this just a TV? If so, put a couple 8" coils in your coax, and you also increase impedance to where lightning won't likely follow it back.
Good Luck,
George
