How would i build or buy a rc car transmitter signal repeater?

i need to make something or buy something that can take in the signal from say, an rc car remote control, and put out that same exact signal in the exact same way that it came from the remote control. im looking to make or buy several so as to make a grid pattern to extend my range in all directions so where ever i am i can activate and control the preverbial rc car. any idea where i could find plans for one or a place where i could buy one?