Get ready to geek out! As Online Clock tells you how Radio Clocks work.
This is actually our second article on radio clocks. Our first article was a Short History of Radio-Controlled Clocks.
Everyone should know that clocks and radios just go together like peanut butter and jelly or Abbott and Costello (OK, I guess I’m showing my age there).
But the subject of this post is not clock radios, but instead the other kind of radio clocks: clocks which update themselves to the correct time using radio signals. Often such radio clocks are referred to as “radio-controlled clocks“.
We often take radio clocks for granted in this day and age, but it wasn’t long ago that people actually had to go through their home or apartment and manually update all of their clocks (and VCRs!) after the switch to or from Daylight Savings Time.
Most of us would agree that radio clocks provide a huge benefit. But did you ever ask yourself how they work?
Well, radio clocks do indeed work with radio waves. They are often known as “atomic clocks“, though this is really a misnomer and have themselves nothing to do with atomic clocks. In most cases, the signal these radio clocks receive from a time station might come from a connection to an atomic clock…but the standard radio clocks we have in our homes nowadays are actually far removed from true atomic clocks!
As mentioned, radio clocks update themselves by receiving continuous time signals from time transmitter stations that send time information over radio waves.
The kind of radio waves involved are usually extremely low-frequency radio waves of about 60,000 Hz that are sent by high-power radio transmitters and therefore reach long distances.
If you’re an extreme geek (and if you are, we love you for it) you can find out more details about the kind of radio signals used for radio clock time transmissions here on the NIST website.
Not familiar with NIST? If you live in the United States, you should be.
NIST stands for the National Institute of Standards and Accuracy and they help determine what accurate time is. If you have a radio clock and live in the United States, your clock is surely updating itself by communicating with NIST’s radio signals.
So then we come, finally, to the question of exactly how these time signals work, so that your clock can update itself.
The time transmitter sends a continuous radio signal to your clock.
But the signal’s power is suddenly greatly reduced for a period of 0.2, 0.5 or 0.8 seconds.
- 0.2 seconds’ reduced signal = a binary zero
- 0.5 seconds’ reduced signal = a binary one
- 0.8 seconds’ reduced signal = a separator
This is all the information a transmitting time signal needs to send to your radio clock in order to indicate the correct time. Much like a computer, the time signal indicates the current time using a binary system of on/off or zeros/ones to communicate.
The time signals sent are so slow-moving that it takes a full sixty seconds to communicate the proper time to your radio clock! However, this can also include information for the current month, year and day of the month, etc…
When we say slow moving, we’re not kidding!
Radio clocks send at a rate of one bit per second. Compare that with an old-fashioned internet modem which sends tens of thousands of bits per seconds. By “bit” we’re referring to a binary state such as a one or a zero.
So now you know the secret of how radio clocks work!
Whatever you do - don’t tell everyone, or they’ll start adding commercials to those time signal broadcasts!
Ovaltine O’Clock, anyone?
Oh, by the way, did you think this story was going to be about another kind of clock radio? If so, visit our internet clock radio right now and compensate for all this geekiness by simply rocking out.
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