How do I combine two video sources on one coax?

splitter.

Actually that's easy. The previous two bozos obviously have had no antenna/cable system training. All you need is a two set 75 ohm coaxial coupler (aka splitter). Run a short piece of coax from TiVo 1 to output A and the other to output B of the coupler. Then connect your TV to the input of the coupler. Simple. The coupler will work just as well at combining signals as it normally does at splitting signals.

You need an A/B switch. You can buy them at any Radio Shack. However, the input select from your TV must be done manually from the A/B switch. There is no device that will allow you to combine the two signals to one feed, allowing you to control it from the input select on your TV. Sorry, I know that isn't what you wanted to hear, but that is the case. Does your TV just have the 1 coax line in? If you have RCA, S-video or other inputs, you could use those, and use the input select on your TV remote. You just can't do it on the single coax line in.

This is a tough one to answer because you did not specify what your source is and what tuner you are using for channels, as well as what kinds of inputs your tv has. Assuming you are using cable with your tv tuner (no cable box) and your tv has only one coax commection (no A/V inputs) then you sould simply use a source selector (turns one coax into several coax or A/V connections). They cost $20-40. They also allow you to connect multiple devices (dvd,vcr, game). If you want, email me with more info and I can help you straighten out your gear.