A Precision Radio Clock for WWV Transmissions

This report describes a software program that functions as a radio clock using shortwave radio signals transmitted by National Institute of Standards and Technology (NIST) radio stations WWV and WWVH. Operated in conjunction with an inexpensive, fixed-frequency shortwave radio, it has nominal timing errors less than 125 μs when tracking one of the stations and frequency variations less than 0.5 parts-per-million (PPM) when not tracking either station. The clock produces an ASCII timecode that can be used to set the time of another device, such as a computer, as well as precision reference signals that can be used for other purposes, such as to drive laboratory test equipment.