UHF TV modulator

Circuits which produce an amplitude modulated VHF or UHF signal from a video input signal have many applications. They allow direct connection to the TV aerial input of such devices as TV games, video biofeedback circuits and test pattern generators, to name but a few. Unfortunately, the performance of most simple modulators leaves much to be desired. However, the circuit described in this article, though extremely simple (one transistor!), offers extremely good performance.