International frequency comparisons by means of standard radio frequency emissions

The Bureau of Standards, Washington, U. S. A., emits from its station at Beltsville, WWV, a few miles from Washington, a standard frequency of reference by which other organizations and individuals can measure the frequency of their own apparatus. The frequency is 5 million cycles per second, and its departure from the nominal value is not expected to exceed 1 cycle per second. The frequency of emission is compared continuously with that of the standard equipment at the Bureau and is monitored so as not to differ from that frequency by more than 1 part in 108 . The value of the frequency has been determined at the National Physical Laboratory, Teddington, on a number of occasions. The observations have afforded information as to the agreement of standards of frequency in the two countries, and show with what accuracy the frequencies of two different standards can be compared by the use of emissions at a radio frequency. Some information is also obtained concerning the effect of the intervening medium on the propagation of an emission at this frequency.