RF Modulator

Hello all.

Can anyone provide an explanation on the workings of these devices which sit in the input line from a TV antenna and split the incoming signal into two parts, one a VHF signal to an older tv set and the other a composite signal to a modern DVD recorder? Not too technical please.

Thanks

In simple terms the VHF signal is created by a small low powered TV transmitter, usually selectable to channel 3 or 4 in the USA. The composite signal is audio(sound) and video(picture)for the DVD recorder.

A TV antenna receives many channels. The channels all have TV transmitters.
You must be talking about a device that selects and demodulates a channel and produces an audio and composite video signal.

Many thanks to you both for your responses. Much appreciated.