1962

Atomic Clock Radio Station

Engineers are known for making society more efficient. So think about this: Every year in the United States, we change our clocks forward and back for Daylight Savings Time. At least twice each year, every clock has to be set.

Now assume 100 million households in America. Assume that every household has one clock that needs setting. Assume it takes a minute to set the clock. Twice a year. How much time is America wasting on clock setting under those assumptions? Almost 400 human years. Is there a way to recover all that lost time?

Engineers answered the question with an ingenious solution. They envisioned clocks that can set themselves. To do it, they use radio waves. There is a radio station in Colorado called WWVB, activated in 1962. It has massive power: 70,000 watts. It has an enormous antenna. It transmits on a very low radio frequency of 60,000 hertz, giving it a great deal of range (especially at night). And it has an incredibly simple AM format: every second it transmits one bit, and every minute a new time code is sent. It also encodes a second phase-modulated signal as well.

With this radio system in place, a clock in your home can contain a simple AM radio receiver and a tiny processor to receive and decode the signal. Then, once it receives the signal, it can display the correct time. Since WWVB gets its time from a NIST-certified (National Institute of Standards and Technology) atomic clock, every clock using this technique has extremely accurate time.

Because of the radio station’s power, antenna, and low frequency, it covers the entire continental United States. At night it can reach out toward Hawaii and South America.

The effect is this: If you buy a clock that can listen for WWVB—it will often describe itself as an “atomic clock” on the package—you can put in the batteries and one of two things will happen. Either, a minute later, it will magically set itself. Or, that night, it will set itself. It depends on how far away you are from Colorado. Engineers just saved you a few minutes of your life every year.

SEE ALSO Mechanical Pendulum Clock (1670), Radio Station (1920), Atomic Clock (1949), Microprocessor (1971).

Radio-controlled clocks are synchronized by a time signal from an atomic clock.