International frequency comparisons by means of standard radio frequency emissions

doi:10.1098/rspa.1935.0078

International frequency comparisons by means of standard radio frequency emissions

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1935.0078 ◽

1935 ◽

Vol 149 (868) ◽

pp. 506-510 ◽

Cited By ~ 5

Keyword(s):

Radio Frequency ◽

National Physical Laboratory ◽

Standard Equipment ◽

Standard Frequency ◽

Physical Laboratory

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 10 8 . 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.

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The valve maintained tuning fork as a primary standard of frequency

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1934.0003 ◽

1934 ◽

Vol 143 (849) ◽

pp. 285-306 ◽

Cited By ~ 14

Keyword(s):

Radio Frequency ◽

Tuning Fork ◽

Primary Standard ◽

Frequency Standard ◽

National Physical Laboratory ◽

Continuous Operation ◽

Normal Value ◽

Rapid Advance ◽

Satisfactory Performance ◽

Physical Laboratory

In 1922 an investigation was carried out at the National Physical Laboratory to determine the constancy of frequency that could be expected from a valve maintained tuning fork. It was found that the fork was capable of operating with a degree of steadiness of frequency which was greater than was then necessary for most purposes. The investigation resulted in the design of a 1000 cycles per second fork which served as the Laboratory frequency standard until 1931. For precision work it was necessary to measure the frequency of the fork during the observations by comparison with a standard Shortt clock ; but if the accuracy required was less than 2 parts in 10 5 it was sufficient to apply a correction for temperature to the nominal value of the fork frequency. With the rapid advance in radio frequency technique and the ever-increasing number of wireless transmitting stations the problem of frequency standardization became increasingly important; and it was decided to instal a standard, which should be in continuous operation at a frequency within I part in 10 6 of its normal value. As the most suitable frequency for use in conjunction with the existing equipment for the measurement of radio frequencies was 1000 cycles per second, and as the tuning fork had hitherto given a satisfactory performance, it was decided to continue the investigation on the fork to determine whether it could form a frequency standard of the desired degree of accuracy.

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