電波時計によるJJYのタイムコードの遅延時間とパルス幅

概要

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One of the JJY stations, placed on Mt. Otakadoya, has been operational since 10 June 1999 with a frequency of 40kHz. A set of time codes modulates the amplitude of LF radiowave by the amplitude shift keying (ASK) so that the time of the radio-controlled clock can be adjusted automatically. The time-codes of JJY signal are sent at a very low rate of 1 bps using pulse width modulation. The authors measured the delay-times of the three kinds of the decoded time-code: 0.2s, 0.5s, and 0.8s. The PPS (pulse per second) signal from the time transfer GPS receiver with accuracy of 1×10-6 and a rubidium frequency standard with a stability of 5×10-11/month were used for the time standard and the delay measurement counter respectively.The delay-times measured for three kinds of time-code sent from the 40 kHz JJY station at a distance about 233 km are 65 ms for pulse-width of 0.2 s, 83 ms for pulse-width of 0.5 s, and 105 ms for pulse-width of 0.8 s. As the propagation delay of standard wave for the distance of 233 km is 0.7 ms, the delay-times obtained are mainly from the crystal filter in the 40 kHz receiver.
2005-08-01