An electronic monitor and system for automatically monitoring broadcast band listening habits and periodically collecting data at a central location. The electronic monitor includes a microphone circuit and a tuner circuit. The tuner circuit is tuned until a match is found between the microphone circuit and the tuner circuit and the event of a match is recorded in the portable monitor. Operation may be performed intermittently to extend battery operation. The portable monitor further has power supply monitoring circuits to prevent incorrect data and loss of data in the event of battery discharge. Digitizing and signal processing circuits are provided to perform the match and loss of match determination.