It may sound like fun to have your own broadcast TV station, but doing so can radiate the modulated signal over the air, and cause problems for legitimate users of that frequency. Always install an amplifier as a buffer between the antenna and any modulator source. Balancing the signal strength of direct off the air and local signals can be a little tricky, especially without fancy test equipment. Luckily, most TV receivers have a wide dynamic range, so this probably won't be a problem. You can buy in-line attenuators in different values to help balance signal sources if you need to.
Splitters also work backwards as combiners.
Forward or backward, splitters introduce signal loss. They do this to keep the impedances of the system constant, and to isolate the inputs or outputs from each other. Some splitters have the loss printed or stamped on them, in units of dB or deciBel. The more outputs the splitter has, or the more splitters are cascaded one after the other, the more loss you will have. Tilt Amplifiers have dB ratings too.