Atomic Timekeeping

Receiving time calibration signals throughout the day from one or more of the six atomic clock transmission stations located around the world, radio-controlled watches and clocks are the most accurate you can own.

Atomic clocks use the isotope Cesium 133 because its atomic frequency can be controlled to regulate the time within 1 second per every million years.  Although we could explain exactly  how atomic clocks work, it is a somewhat complicated process.  Six of these clocks (located around the world) have transmission stations which enables radio-controlled timepieces to update the time via radio signal.

Below are some map images from Casio’s G-Shock website showing these six atomic clocks and their range around the world:

Some radio-controlled devices fully rely on the radio signal, while others can be used like any other quartz timepiece (you will have to check with the manufacturer of the product to see if it will operate without a signal).  If a radio-controlled timepiece loses a signal, it should continue to tell the time accurately.  However, there are some things which you should be aware of that may prevent your watch or clock from receiving a signal:

  • Mountainous regions
  • Remote locations
  • Adverse weather conditions
  • Computer monitors and other devices which may disrupt a radio signal
  • Shielding such as a  metal building or thick walls

Sometimes the placement of radio-controlled clocks in the home can prevent them from receiving signals.  If this happens, simply put the clock near a window until it is able to receive an initial signal.  Once it adjusts the time according to the signal, it can then be put back where it was.

Manufacturers such as Casio and Citizen have several different radio-controlled watches to chose from, while other manufacturers such as Seiko and Bulova have unique, radio-controlled clocks.  Whether you prefer the precision of the Citizen Skyhawk or AT collections, or the durability of the Casio G-shock, Pro Trek, or Edifice collections there is an atomic watch out there for everyone.

To place an order or to view our entire collection of radio-controlled timepieces, visit us at

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