The standard frequency monitor at the National Physical Laboratory

Abstract
Equipment has been constructed at the National Physical Laboratory for the automatic measurement and recording of the standard frequencies transmitted by MSF, Rugby, on 60kc/s, 2.5, 5 and 10Mc/s, and also the carrier frequency of Droitwich, 200kc/s. For the latter and MSF 60kc/s, the methods of measurement are an extension of those already well established for the intercomparison of the N.P.L. frequency standards. The standard deviation of measurements lasting a few seconds is 2–3 parts in 109 for MSF 60kc/s, and 3–4 parts in 109 for Droitwich.Measurements of the phase of the 1c/s pulse modulation on MSF 60kc/s can be made with very high precision. In daily comparisons, the scatter of a group of 60 readings does not usually exceed 30microsec.By a process involving frequency changing by continuous phase shifting, the received frequencies of MSF 2.5 and 5Mc/s are recorded on a frequency meter of range ±1c/s, the discrimination being 2 parts and 1 part in 108 at these frequencies, respectively. The records obtained show well-defined diurnal variations on 2.5Mc/s, particularly at sunrise, where the deviations may amount to several parts in 107. The received frequency of 5 Mc/s is subject to continuous variations over a range of about 1 part in 107 during daylight hours; in darkness larger changes are recorded.
Keywords

This publication has 0 references indexed in Scilit: