Recent Activities on Time and Frequency at the Radio Research Laboratories

Abstract

The recent activities on time and frequency at the Radio Research Laboratories (RRL), Tokyo are briefly summarized in the following outline:

(i) Atomic time scale: Two algorithms for calculating a highly uniform time scale have been developed in order to establish TA(RRL), and the results of the comparison between TA(RRL) and the time scales of foreign organizations are given. (ii) Dissemination of standard frequency and lime signal: A brief description on the measuring and controlling system of the standard frequency and time signal transmissions, JJY (MF and HF) and JG2AS (40 kHz) is given. (iii) T and F satellite experiments: International time-transfer experiment via Navigation Technology Satellite (NTS-1) showed the accuracy of several hundred nanoseconds. Besides, simple correction for ionospheric time delay ruduced the standard deviation by 30% compared with that of the raw data. Experiments of the dissemination of frequency and time were made in 1979 and also in 1980 using the experimental broadcasting satellite and the accuracy capability of smaller than 1 ×^-10^-11 in frequency and 1 μs in time was confirmed, (iv) Atomic frequency standard: Long-term operation of two hydrogen masers has been made over one year. Short-term and long-term frequency stabilities with the automatic cavity tuning are about 7 × 10^-15 and 2 × 10^-14, respectively.

Besides, the Majorana effect on the atomic-frequency standards has been studied. For the caesium beam standard with hexapole magnets, this effect was removed successfully. For a hydrogen maser using the double focussing method and the Majorana transition, we could remove about 75% of F = 1, mf = 1 atoms, and observed the increase of 50% in the oscillation power and also the decrease of the line width.