Simplified Time-Signal Receiver

60 EE November 1988 SIMPLIFIED TIME-SIGNAL RECEIVER The automatic synchronization facility of many microprocessor- based clocks ensures reasonable long-term accuracy even when the relevant time-signal transmitter is received for only a couple of minutes each day. Obviously, this feature relaxes the design requirements of the receiver, which can be kept relatively simple. Such a receiver is described here: it has a digital pulse output, excellent sensitivity, and can be tuned to time-standard stations transmitting in the VLF band between 50 and about 100 kHz. Time-signal transmitters such as Rugby MSF, HBF and DCF77 operate in the VLF (very low frequency) band, at fre- quencies between 50 and 100 kHz. The VLF band is characterized by very predictable propagation characteristics, but received signals often suffer from in- terference generated by electrical ap- paratus such as TV sets and dimmers. The receiver should, therefore, have good or very good selectivity. The fre- quency con...