RF Modulators can be useful for several reasons. Suppose you have an old TV without Scart or phono connections. You can watch TV on it but that's about all. You can't use a games console, a set top box, a camcorder etc. By using a RF Modulator you can modulate the signal from a Scart or phono device so that it can be connected to a RF aerial. RF Modulators can also used to convert and send send satellite, Freeview, VCR or DVD signals TV around a home on RF coaxial aerial cable.