Where can I purchase a grounding rod. I have to cable installed and was told to install a grounding rod

Do you mean you are having cable TV installed?
Will this be for a building that already has an electric service?

Please provide more detail.

You should not just install one ground rod for CATV system, it needs to be grounded to the groudning system already in the building.

If this is being done by a CATV utility, or even a dish provider, that installer is suppose to know how to ground his system properly.

HD and Lowe's carry them. They are Copper clad steel, do not use rebar. Get ready for some hammering and hope your soil is fairly soft. You should have one already at your house though, or you can use a cold water pipe as long as it is copper or steel, not plastic.

Kburbank, I need to caution you, now that you been informed where to purchase ground rods, I asked you some questions about what your doing, because, you cannot, should not, just install a ground rod for a single device, such as a satellite dish, or CATV service.

Your CATV or Dish installer should know how to ground his system, without having the homeowner install a ground rod.