Every night, while millions of Americans are fast asleep, clocks and wristwatches across the country wake up and lock on to a radio signal beamed from the base of the Rocky Mountains. The signal contains a message that keeps the devices on time, helping to make sure their owners keep to their schedules and aren't late for work the next day.

The broadcast comes from WWVB, a station run by the National Institute for Standards and Technology. WWVB marks half a century as the nation's official time broadcaster on July 5. Together with its sister station, WWV, which is about to hit 90 years in service, NIST radio has been an invisible piece of American infrastructure that has advanced industries from entertainment to telecommunications. (WWV's broadcast includes a wider range of information, including maritime weather warnings and solar storm alerts).

Most people aren’t even aware that these stations exist, but they have a rich and fascinating history. Their future is uncertain, however, as newer technologies threaten to make them obsolete.

NIST is the government agency charged with developing the technology standards that underlie everything from data encryption to cholesterol tests. “We’re in the business of weights and measures,” said John Lowe, who directs NIST’s time services from Boulder, Colorado.

At first glance, it’s unclear why the people who test bulletproof vests and smoke detectors would be in the radio business. But as broadcast technology blossomed through the first half of the 20th century, the government quickly recognized the need to standardize radio. Manufacturers were churning out equipment left and right to deliver information over the air, but no one was ensuring that a particular frequency was the same in Maine as it was in Malibu.

Enter NIST, the folks who determine the length of a second. A radio signal is really defined by time, the number of peaks in a wave that pass by a point every second. The FM band, for instance, occupies the airwaves between 87.7 and 108 megahertz (MHz), or millions of cycles per second. Making sure that the dial on the radio in someone's home or car matches the broadcast signal demands that stations and receivers all agree on the same standard second.

Credit: The rear viewing lens (photo by Roy Wood)

WWV began broadcasting reference frequencies for signal calibration using equipment not that different from the chunk of quartz in a modern wristwatch. These days, though, a bit of quantum physics keeps the nation’s signals in sync. Cesium-133 atoms within the NIST-F1 atomic clock oscillate a frantic 9,192,631,770 times per second, acting like the pendulum of a grandfather clock. By tuning into that oscillation, NIST defines the basic unit of time, and by extension, frequency. Over the years, the reference frequencies have been so finely calibrated that they are accurate to beyond a single cycle in a trillion.

Thanks to this ability to fine-tune broadcasts, AM and FM commercial radio exploded during the 1960s and '70s because more precise signals meant that more stations could be crammed into a particular range of frequencies. Listeners now had access to more music and programming than ever before. In a way, Lowe says, rock 'n' roll owes a small debt to the atomic clock.

In 1965, two years after going on the air, WWVB set out on a new mission to broadcast accurate time to the whole country. This seems downright quaint in an age when one can broadcast a photo of a sandwich halfway around the world in less than a second, but at the time it was revolutionary. Radio-controlled clocks let Wall Street traders certify stock trades down to the second, and power plants could avoid brownouts caused by out-of-sync switches. Heathkit, a popular manufacturer of hobby electronics kits, even sold an “atomic clock” you could build at home. It wasn't a true "atomic clock" of course, but it did receive a signal from one. Those were high times for time radio.

Then came the internet. And then GPS. The very industries that WWVB helped build suddenly threatened to make it obsolete.

Today, stock traders rely on computerized trading algorithms that measure success in milliseconds, choosing to synchronize their servers with NIST’s internet-based time service instead of WWVB. And since GPS satellites carry their own atomic clocks, nearly all of today's time and frequency needs are served from space. For proof, look no further than the phone in your pocket, delivering time beamed down from orbit.

Despite these challenges, Congress thinks NIST’s time radio broadcasts are still essential to national infrastructure and recently granted $16 million for signal enhancements (Lowe says they only used $100,000 and were proud to return the rest).

WWVB’s value might have a lot to do with the type of signal it broadcasts and its location. While most commercial radio waves measure only a few meters between peaks, WWVB’s low frequency signal results in a whopping five kilometer wavelength. These long-wavelength signals can reach around the curvature of the planet by clinging to the semi-conductive surface of the Earth. On a clear night, a radio-controlled watch can pick up WWVB’s 60 kHz signal as far away as Patagonia or New Zealand.

Credit: The infra-red emitter (top) and main lens with cap (bottom)

The electromagnetic weirdness doesn’t stop there. Large wavelengths require large broadcast antennas, and NIST's signal relies on a wire mesh suspended over their 400 acre antenna field. The soil chemistry beneath the antenna grid outside Fort Collins, Colorado is highly alkaline, which makes it a good conductor for electricity. Because it conducts so well, NIST can actually use the Earth as part of their antenna.

The ability to put out a continent-spanning time broadcast, Lowe explains, is what has kept WWVB going this long. Inexpensive clock radios and wristwatches, marketed as “atomic clocks”, could be set each night by NIST’s master signal. Yet despite this promise, radio-controlled timekeeping these days is mostly relegated to nightstand novelties.

But Lowe thinks that NIST’s time radio will continue to find new uses. “Imagine all the alarm clocks in a hotel,” Lowe explains. “They are notoriously wrong.” WWVB’s newly amped up time signals can penetrate buildings with ease – something that can't be said for GPS.

Lowe foresees a new world of applications for his time broadcast. Out of sync traffic lights will keep traffic flowing. Sprinkler systems will be immune to Daylight Savings errors, conserving water and avoiding penalties caused by watering during prohibited times. The eternally imminent “wired home of the future” will rely on every appliance and electronic device knowing exactly what time it is, and Lowe insists the days of clocks blinking “12:00” could be a thing of the past.

Despite these possibilities, it remains to be seen if WWVB can stay ahead of ever-cheaper GPS technologies.

The time-impaired should rest assured that even the folks behind WWVB don’t always keep perfect time. WWVB broadcast engineer Matt Deutch admits he is sometimes late. "But I know exactly how late I am," he said.

The ubiquity of mobile phones means that most people now look to their pocket or purse instead of their wrist when asked for the time. As essential as time is to their lives, most Americans simply don’t think about, where it comes from, only that it’s always there. When it comes to keeping Americans on schedule, WWVB has quietly succeeded for half a century. As for what the future holds, only time will tell.

This post has been edited to correct the explanation of how long-wavelength radio waves travel long distances.