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Stability of GPS and GLONASS onboard clocks on a monthly basis

100%

Ziętala M.

tom z. 114

193--209

This paper presents the stability of the GPS and GLONASS system clocks’ stability. It describes the construction of these two systems and calculated four different Allan variances (AVAR), based on the MGEX (the Multi-GNSS Experiment) clock products. Four used variances allowed making a better analysis of each GNSS system clock. The results are shown at different averaging times from 5 s as successive multiples to 655,360 s in a monthly period. The stability of GPS and GLONASS clocks is included in the range of 10-12~10-14 s. The results showed that GLONASS clocks are stable (10-12~10-14 s) and are affected with white frequency noise (WFM). The GPS clock stability models have more fluctuations for τ > 40,960 s and the mean stability is concluded between 10-12~10-13 s. Mean frequency accuracy for GPS clocks is related with WFM and Random Walk Frequency (RWF). The differences in clock stability are caused by several factors – block type, type of clock and the time of a satellite in orbit. These factors have an influence on stability results.

O czasie i zegarach. Część II

80%

Dobrogowski A.

tom nr 4

271-277

Jest to druga część artykułu, w której opisano poglądy na początek Wszechświata, przywołano ważne daty jego historii i wskazano warianty jego możliwej przyszłości. Rozważano problematykę rachuby czasu za pomocą kalendarzy i zegarów. Przedstawiono astronomiczną i atomową skalę czasu.

This is the second part of the paper, which some ideas for the origin of the Universe, the important events from its history and some variants its possible future arę discussed in. Time count using calendars and clocks is considered. Astronomical and atomie time scales arę addressed.

GNSS-based sound card synchronization

70%

Carôt A. , Mahmood H. , Hoene C.

2019

tom Vol. 18

309-–312

Audio communication on the public Internet suffers from not synchronized word clocks of the involved audio devices. The resulting clock drift leads to audio dropouts, which is typically compensated by a sample rate conversion (SRC) in standard telecommunication systems. This, however, does not fulfill the requirements of a high-quality audio system, in which all devices share one and the same word clock. Professional IP based network audio systems such as DANTE or AVB with their respective clock synchronization techniques have so been limited to LAN usage, where network jitter and loss have negligible importance regarding the required accuracy in the dimension of several nanoseconds. In a WAN, however, jitter in the millisecond dimension would lead to unacceptable measurement errors for the intended clock synchronization. As a consequence, we decided to investigate alternative clock synchronization techniques for WAN-distributed devices and developed a GNSS-based approach, which leads to precise clock synchronization.

Sztuka odmierzania czasu

60%

Bielski M. W.

tom nr 1 (5)