Standard Frequency Broadcast Service of National Bureau of Standards
June 1945 Radio News

June 1945 Radio News

[Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919-1959. All copyrights hereby acknowledged.

According to the National Bureau of Standards' (now National Institute of Standards, NIST) website, In October 1949, Congress authorized $4.5 million for "the construction and equipment of a radio laboratory building for the National Bureau of Standards," for the planned new location of WWV in Ft. Collins, Colorado. WWV was initially established in 1919 in Washington, D.C., later moved to Beltsville, Maryland, then finally relocated to Ft. Collins, Colorado, in 1955. Construction began on the facility in 1951 and was dedicated in September 1954 by President Dwight D. Eisenhower. This item from the June 1945 issue of Radio News magazine reports on the Colorado location, with WWV's addition of a 15 MHz time standard broadcast.

Here is an extensive paper on the history of WWV entitled "A Century of WWV," by Glenn K. Nelson, in Journal of Research of the National Institute of Standards and Technology. See also "WWV Moves to Colorado," January 1967 QST.

Details and description of the entire broadcast service emanating from station WWV.

This service comprises the broadcasting of standard frequencies and standard time intervals from the Bureau's radio station WWV near Washington, D. C. Starting in Feb., 1945, the service was slightly extended by broadcasting 15 megacycles at night as well as in the daytime.

The service is continuous at all times day and night, from 10-kilowatt radio transmitters except on 2500 kilocycles per second where 1 kilowatt is used. The services include: (1) standard radio frequencies, (2) standard time intervals accurately synchronized with basic time signals, (3) standard audio frequencies, and (4) standard musical pitch, 440 cycles per second, corresponding to A above middle C.

The standard frequency broadcast service makes widely available the national standard of frequency, which is of value in scientific and other measurements requiring an accurate frequency. Any desired frequency may be measured in terms of the standard frequencies. This .may be done by the aid of harmonics and beats, with one or more auxiliary oscillators.

Four radio carrier frequencies are used; three are on the air at all times, to insure reliable coverage of the United States and other parts of the world. The radio frequencies are listed in the table.

Two standard audio frequencies, 440 cycles per second and 4000 cycles per second, are broadcast on the radio carrier frequencies. Both are broadcast continuously on 10 and 15 megacycles. Both are on the 5 megacycles in the daytime, but only the 440 is on the 5 megacycles from 7:00 P.M. to 7:00 A.M., EST. Only the 440 is on the 2.5 megacycles.

The 440 cycles per second is the standard musical pitch, A above middle C; the 4000 cycles per second is a useful standard audio frequency for laboratory measurements.

In addition, there is on all carrier frequencies a pulse of 0.005−second duration which occurs at intervals of precisely one second. The pulse consists of five cycles, each of 0.001−second duration, and is heard as a faint tick when listening to the broadcast; it provides a useful standard time interval, for purposes of physical measurements, and may be used as an accurate time signal.

On the 59th second of every minute the pulse is omitted.

The audio frequencies are interrupted precisely on the hour and each five minutes thereafter; after an interval of precisely one minute they are resumed. This one-minute interval is provided in order to give the station announcement and to afford an interval for the checking of radio-frequency measurements free from the presence of the audio frequencies. The announcement is the station call letters (WWV) in telegraphic code (dots and dashes), except at the hour and half hour when a detailed announcement is given by voice.

The accuracy of all the frequencies, radio and audio, as transmitted, is better than a part in 10,000,000. Transmission effects in the medium (Doppler effect, etc.) may result at times in slight fluctuations in the audio frequencies as received; the average frequency received is, however, as accurate as that transmitted. The time interval marked by the pulse every second is accurate to better than 10 microseconds (0.000010 seconds). The 1−minute, 4−minute, and 5−minute intervals, synchronized with the seconds pulses and marked by the beginning or ending of the periods when the audio frequencies are off, are accurate to a part in 10,000,000.

The beginnings of the periods when the audio frequencies are off are so synchronized with the basic time service of the U. S. Naval Observatory that they mark accurately the hour and the successive 5−minute periods.

Of the radio frequencies on the air at a given time, the lowest provides service to short distances, and the highest to great distances. Reliable reception is in general possible at all times throughout the United States and the North Atlantic Ocean, and fair reception throughout the world.

Information on how to receive and utilize the service is given in the Bureau's Letter Circular, "Methods of using standard frequencies broadcast by radio," obtainable on request. The Bureau welcomes reports of difficulties, methods of use, or special applications of the service. Correspondence should be addressed National Bureau of Standards, Washington, D. C.

Posted July 19, 2021