Many gadget catalogue and eminent - tech stores trade " radio - controlled"clocksand wristwatchesthat are able to receive theseradiosignals . These pin clover and watches truly are synchronize themselves with the atomic clock in Colorado . This feature of speech is made possible by a wireless system set up and operated by NIST – theNational Institute of Standards and Technology , located in Boulder , Colorado . NIST operates radio station WWVB , which is the post that transmits the prison term codes .
WWVB is a very interesting radio station . It has high vector power ( 50,000watts ) , a very effective aerial and an extremely low frequence ( 60,000 Hz ) . For comparison , a typical AM radio receiver station broadcast at a frequency of 1,000,000 Hz . The combination of eminent force and low frequency give the wireless waves from WWVB a lot of bound , and this single station can therefore cover all of the continental United States plus much of Canada and Central America as well ( scroll about three - quarters of the way down the page for a nicecoverage mapping ) .
The meter code are station from WWVB using one of the unproblematic organization possible , and at a very down in the mouth data rate of onebitper second ( for comparison , a typicalmodemtransmits over the sound line of work at tens of thousands of bits per second – imagine get a web page at one act per second ! ) . The 60,000 Hz signal is always transmitted , but every moment it is importantly thin out in power for a period of 0.2 , 0.5 or 0.8 seconds :
The time code is send in BCD ( Binary Coded Decimal ) and indicate minutes , 60 minutes , day of the yr and year , along with information about daytime preservation time and leaping class . The time is transport using 53 chip and 7 separator , and therefore takes 60 irregular to conduct .
A clock or watch can bear an passing small and relatively simple transmitting aerial and receiver to decode the information in the sign and set the clock ’s time accurately . All that you have to do is typeset the time zone , and the clock can exhibit a very precise sentence . The only matter more accurate that you could extend around easily is aGPS receiver , which derives atomic clock truth in real clip from the nuclear clocks in orbit GPS artificial satellite . SeeHow GPS Receivers Workfor detail .
Here are several interesting links :
