Atomic Alarm Clock

How they work and how to keep them working.

The name may sound impressive, but an atomic alarm clock is not actually an atomic alarm clock. The term is a misnomer. Atomic alarm clocks are properly referred to as radio controlled alarm clocks. True atomic clocks operate using an atomic oscillator, but the standard "atomic" clocks and "atomic" alarm clocks used in American homes synchronize via a radio signal received from a true atomic clock located in Colorado.

How atomic alarm clocks work

Despite not being true atomic alarm clocks, radio-controlled alarm clocks are still extremely accurate. If it's working properly, your atomic alarm clock will synchronize the time it displays at least once a day with a true atomic clock.

The radio signal your atomic alarm clock uses to keep time is a 60 kHz signal sent from the National Institute of Standards and Technology, a U.S. Department of Commerce agency located in Boulder, Colorado. The NIST atomic clock is in Boulder, but the radio signal it sends is transmitted by radio towers in Fort Collins, Colorado. This NIST radio station is known by the call letters WWVB.

When it's first set up, your atomic alarm clock will need to acquire the WWVB signal. You will also have to indicate what time zone you reside in. As it's setting up, your atomic alarm clock may display an antenna icon on its LED display to signify that it's searching.

Once the WWVB signal is acquired, the atomic alarm clock will set its time in conjunction with the NIST atomic clock. So long as it can maintain radio contact, your atomic alarm clock will synchronize with NIST 1 to 4 times a day. And since the NIST atomic clock is accurate to within ten billionths of a second, the time displayed on your atomic alarm clock will be nearly as accurate as it's possible to get.

Atomic alarm clock problems

Atomic alarm clocks keep very accurate time, but some people experience a problem with radio signal interference. If that occurs, your atomic alarm clock will continue to keep time using a quartz crystal oscillator, but will gradually drift further away from the true time.

To avoid this problem, position your atomic alarm clock away from computer monitors or other items that might cause signal interference. If you notice that the time is off on your atomic alarm clock by seconds or minutes, it has likely lost the signal. Possible causes of a lost signal are low clock batteries, local signal interference, or steel siding.

If your atomic alarm clock is off by several hours, it's very likely set for the wrong time zone. The time discrepancy could also be caused by changes in Daylight Savings Time. Check to see if DST is enabled or disabled on your atomic alarm clock to resolve that problem.

Traveling outside of the continental U.S. could also prevent your atomic alarm clock from working. Different radio frequencies are used for such clocks in Europe, and in Hawaii you may not be able to pick up the signal at all. But then if you're in Hawaii, chances are it's a vacation and you'll be sleeping in anyway.

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