Automatic equalization for simulcasting

Abstract

The simultaneous transmission of the same audio from several conventional FM base stations over a wide area has been known to provide operational advantages and performance improvement in many cases. The technique has seen limited application, however, due to the requirement of stable microwave audio links to each of the base stations. A system that circumvents this requirement is described. Automatic equalization periodically compensates for changes in amplitude response and phase delay, allowing operation over conventional private lines leased from the telephone company. The system uses these same facilities to synchronize continuous tone-coded subaudible squelch (CTCSS). The simulcast electronics interfaces to the dispatch system through a microcomputer that also controls the signalling subsystems, providing the dispatcher with the ideally simple "push-to-talk" operation.