Time signals and audio frequencies are broadcast continuously day and night from WWV, operated by the National Bureau of Standards at Fort Collins, Colorado 80521. The WWV broadcast frequencies are 2.5, 5 10, And 15 MHz and The 1-second marker tone consists of a 5-millisecond pulse at 1000 Hz. A similiar station, WWVH, is located at Kekaha, Kauai, Hawaii. It broadcasts on frequencies 2.5, 5, 10, And 15 MHz and the 1-second marker tone consists of a 5-millisecond pulse at 1200 hz.
The broadcasts of WWV may also be heard by the use of the telephone by dialing (303) 499-7111. The telephone user will hear the live broadcasts from The station called. With the instabilities and variable delays of propagation, The accuracy of the telephone time signals will not be better than 30 milliseconds. This service is automatically limited to three minutes per call.
Station WWVB broadcasts on a frequency of 60 KHz. The station broadcasts a time code continuously. No voice announcements are broadcast from WWVB.
WWV and WWVH broadcast frequencies are consistent with the internationally agreed time scale coordinated universal time (UCT). These changes became effective January 1, 1972. This coordination provides a more uniform system of time and frequency transmission throughout the world. It also aids in the solution of many scientific and technical problems such as radio Communications, geodesy, navigation, and tracking of artificial satellites. At WWV and WWVH, the carrier and modulation frequencies are derived from cesium-controlled oscillators.
Standard audio frequencies of 440 Hz, 500 Hz, and 600 Hz are broadcast on each radio carrier frequency by WWV & WWVH. The 600 Hz tone is broadcast during the odd minutes by WWV and during even minutes by WWVH. The 500-Hz tone Is broadcast during alternate minutes unless voice announcements or silent periods are scheduled. The 440-hz tone (good for calibrating "perfect A" musical strobotuners) is broadcast beginning two minutes after the hour at WWV and one minute after the hour at WWVH. The duration of each transmitted tone is approximately 45 seconds.
The frequencies transmitted from WWV are accurate within .000000000001 Hz. (Incredible as it may seem!) A voice announcement of coordinated universal time is given during the last 7.5 seconds of every minute in the form "At the tone ----- hours ----- minutes coordinated universal time."
Now, onward to the good stuff...
"Hidden" within the WWV & WWVH broadcasts is an encoded time sequence broadcast continuously on a 100-Hz subcarrier. To hear these broadcasts on an ordinary shortwave radio, I constructed some phase-locked-loop circuitry to "decode" the 100 Hz subcarrier. (Much in the same manner as SCA adaptors work on an FM radio). Once the audio is decoded, the time signal can be heard as a binary coded decima, (bcd). Each minute contains 7 bcd groups: 2 groups for minutes, 2 groups for hours, and 3 groups for the day of year. The binary-to-decimal "weighing" scheme is 1-2-4-8 with the least signigicant Binary digit always transmitted first. A binary 0 pulse consists of exactly 17 cycles of 100-Hz amplitude modulation (200 milliseconds duration) and a binary 1 pulse consists of 47 cycles of 100 Hz (500 millisecond duration).
Within a time frame of one minute, enough pulsas are transmitted to convey in bcd, the current minute, hour, and day of year. Hours are expressed 00 thru 23 and day of year is expressed 001 thru 366. In my experimentation, all the further I was able to procede was to manually count the pulses and (hopefully) properly decode them. The actual encoding system is much more complex than I Have outlined here and can be obtained by writing directly to WWV.
Of interest is a new (approx. $450) "clock" available from Heathkit which receives the broadcast from WWV, and decodes the subcarrier signal to display super-correct time on a led display. Incredible! It even sets itself when you turn it on and tune in WWV. Propagation is even corrected for! (Approximately)
For more information on WWV and universal coordinated time, write to
WWV
National Bureau of Standards
Fort Collins, Colorado 80521
Or refer to the Handbook of Electronic Tables & Formulas
Howard W. Sams Publications
Or the ARL Amatuer Radio Handbook
published anually
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Another original phile from Video Vance & Pirate-80 Systems
