Before cable television, before VCRs, the only thing we hooked up to our TVs was an antenna. Then came the Magnavox Odyssey and Atari Pong!
There are two easy ways to get your Atari connected to your TV. You may already have the parts for one, the other takes an adapter but gives a better picture. The pictures below show you everything.
This requires no hardware modification of the system. There are two ways of getting the job done. I'll describe both, and I'll save the background info on why this is such a pain for Page 2.
If you have the TV/Game switchbox that came with the Atari console (or another one just like it) you can get an adapter that goes between the twin screw lugs and your TV's VHF antenna/cable input. The screw lugs are the copper U-shaped thingies at the end of the flat piece of two-wire cable sticking out of the switchbox.
The adapter you need is commonly available at electronics stores, it's usually with the TV antenna equipment and it typically costs less that US$5 retail, usually closer to US$3. It's called a 300-ohm matched pair to 75-ohm F-Connector transformer, in technical jargon. All you really need to remember is that it goes from a pair of screw terminals to an F Connector. The sort you need looks like a little block with a pair of screws on it, on the opposite side is a push-on F connector.
Connect the screw lugs to the adapter's screw terminals (loosen the screws on the adapter, put the lugs underneath, and tighten the screws down on them.) Then push the adapter onto a VHF or antenna input on your TV. The video from the Atari will be on the channel selected on the Atari console (usually either channel 3 or channel 4.)
Here's another way to hook up using the switch box. It's not nearly as nice as the method described above, but it works and you may already have the parts on hand. The game hooks up to the RCA input jack on the top of the switchbox, the twin-lead switchbox's output is connected to a more common type of 75 ohm to 300 ohm transformer (also called a 'balun', which is the specific type of the transformer). I've used a terminal strip here, but you can just use a couple of screws and nuts to connect the lugs, then wrap them in electrical tape to keep them from shorting out. Then you connect the 75 ohm side of the transformer to the TV's antenna input with a standard F-connector cable.
If you don't have the switchbox, then you need a different type of adapter that is less common than the sort used in Method One. This adapter goes from the RCA connector that comes out of the Atari and goes to an "F" connector for the VHF antenna/cable input on your TV. Since there are fewer connections between the Atari and the TV this method will usually give cleaner video than connecting through the switchbox. So even if you have a switchbox you may want to set it aside and connect with one of these adapters.
The adapter is called an RCA Phono Plug to F Jack adapter. A television or satellite TV store would be a likely source for the adapter. Here are some possible suppliers for the adapter: