Development of Precision Time and Frequency Comparison System Using a Broadcasting Satellite

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We may compare time and frequency precisely over long distance by using a synchronization pulse and color subcarrier in a television signal. The purpose of this research was to realize precision time and frequency comparison by means of a satellite broadcasting television signal. We obtained the following results.1. Time comparison was carried out between Hokkaido University ( Sapporo ) and the Radio Research Laboratories, Ministry of Posts and Telecommunications ( Tokyo ) using the broadcasting satellite BS-2a. We corrected the delay time difference of both measurement systems. Furthermore, we corrected the difference of propagation delay time from the broadcasting satellite using predicted orbital data. Then, it was shown that the accuracy of about 0.1 <micro> sec is achieved by the broadcasting satellite. It was also shown that if we use the same measurement system in both of the receiving points, the precision of about 10nsec is realized.2. Frequency comparison was carried out between Hokkaido University and Kagoshima University ( Kagoshima ) using the broadcasting satellite BS-2a. The Doppler shift arises because the broadcasting satellite drifts around the geostationary orbit. The Doppler shift values are different in Sapporo and Kagoshima. Then, the frequency comparison error ( df/f ) amounts to a few parts in <10^(10)> due to the residual Doppler shift. However, it was shown that if we correct the measured results using the predicted orbital data of the broadcasting satellite, the error is in the order of <10^(-11)> .3. This comparison method is realized by inexpensive satellite broadcasting receiving sets and simple pulse and subcarrier extractors. Then, it may be said that the method is advantageous from the view point of economy and widespread availability.