U.e So D».A.RnoDNT 01 COMMEROEe Aug. 

NATIONAL :aURJl:Au.or STANDAliDSe

W'ASHING'l'ON 

STANDA.BD �UENCY BROADCAST SIRVICI 

OF NATIONAL BUREAU OF STANDARDS. 

The National Bureau of Standards broadcasts standard frequencies 

and related services from its radio atation WV, at Beltsville, Md o , near Washingtone0 D.C. The aervice has been improved and extended, a 

new transmitting station has been built, 10--kilowatt radio traneemittera 

installede0 and additional frequ.anclea and voice announcements added. 

The service• include: (1) standard radio frequencies, (2) standard 

time intervals accurately synchronized with basic time1 signals, (3) 

standard audio frequencie1e0 (4) standard musical pitch, 44o•cycles 

per second, corr.espondin& to A above middle C. 

The atandard frequency broadcaat service makes widely available 

the national atandard of frequency, which ia of value in acientific 

and other measurements requiring an accurate frequency. Aey desired 

frequency may be measured in terms of� one of the standard frequenciese0 either audio or radio. Thia may be done by the aid of harmonica and beats, with one or more auxiliary oscillators. 

I 

The service is continuoua at all time•� and night. The atand= 

ard radio frequenciea ares 

5 �egacycles (g 5000 kilocycle•� 50000e0 000 cycles) per second, 

broadcast continuously. 

10 megacycles(� 10e0000 kilocycle•= 10,000e0000 cycles) per seconde0

broadcast continuously. 

15 megacycles(� 15e0000 kilocycles= 15,000e0 000 cycles) per aeconde9 

broadcaat continuously in the daytime only (i.e •• day at 

Washington, D.C.). 

All the radio frequencies carry two audio frequencies at the same 

time, 44o cycles per second and 4ooo cyclea per eecond; the former is 

the standard musical pitch and the latter is a useful etandard audio 

frequency. In addition there ia a pule, every seconde0 heard as a 

faint tick each second when li etening to the broadcaat. The puleeet 

last 0e0 005 second; they may be used for accurate time eigu.11e0 and 

their one=second spacing provides an accurate time interval for purposes of physical meaaurementa. 

The audio frequencies are interrupted precisely on the hour and 

each five minutes thereafter; after an interval of preci1ely one minute 

(over) 

1, 1943 
-2-

they are reaumed. Thie one-minute intenal ia provided in order to give 

the atation announcement and to afford an intenal for the checking of 

radio.-frequeney measurement• free from the presence of the audio frequencieeo The announcement i• the 1tation call letters (WWV) in telegraphic 

code (dots and dashes) except at the hour and half hour when the annowa.cement is given by voiceo 

The accuracy of all the frequencies, radio and audio, aa tranamitted, 

ie better thaa a part in 10 1000 00000 Trsnami11ion effect• in the medium 

(Doppler effect, etc.) may result in alight fluctuatioa1 ia the audio frequencie1 ae received at a particular place; the average frequency received 

is however ae accurate ae that tranemitted. The time intenal marked by 

the pulse every second ie accurate to OoOOO 01 second. The 1-minute, 

4-minute 0 and 5-•iaute iatenale, s7achroaised with the eecoade pul1e1 

ud marked bf the begiaaing aad ending of the period• when the audio 

frequeaciea are off, are accurate to a part in 10 0000 0000. The beginnings of the periods whea the audio frequencies are off are so synchronized with the basic time service of the U.S. Naval Observatory that 

they mark accurate11 , the hour and the successive 5-minute ·periodso 

Of the radio frequencies on the air at a given time, the lowest provides eervice to ehort diataaces, and the higheat to great distan.cea. 

For example 0 during a wiater day good eerTice ie given on 5 megacycle■ 

at distances from O to about 1000 mile1 1 10 megacycles from about 6oo to 

3000 miles, aad 15 megacycle• from about 1000 to 6000 mileso •cept for 

a certm.a period at night 0 within a few hundred milee of the station. 

reliable reception ie in general possible at all times throughout the 

United States and the Borth Atlantic Ocean0 and fair reception over most 

of the world. 

Information on how to receiTe aad utilize the service is given in 

the Bureau 1 e Letter Circular. •Methods of using standard frequencies 

broadcast by radio1

0 obtainable on request. The Bureau welcomes re� 

ports of difficulties 0 methods of uee, or 1pecial application• of the 

serviceo Correspondence should be addressed National Bureau of Standards0 Washing\oa, DoCo