Accurate Timekeeping With Radio Clocks

Different from clock radios, radio clocks are clocks without a built-in AM/FM radio.  Radio clocks are known for keeping accurate time. These clocks are synchronized via a time code bit stream. This stream is then transmitted through a radio transmitter, which is connected to a specific time standard, such as an atomic clock. 

Atomic clocks do not use atomic energy or radioactivity to operate. Instead, they use microwave signals and are considered the most accurate of all time keeping devices. Therefore, radio clocks are set to receive their time from atomic clocks.

Atomic time is synchronized and sent to radio clocks via single transmitters or multiple transmitters. The single transmitter radio clocks are synchronized with radio station signals. They have a precise accuracy rate in relation to the time standard from which it receives the time. This rate is limited by variables in radio air wave transmissions (propagation). 

The multiple transmitters provide more accurate time and use the Global Positioning System (commonly known as GPS). These transmitters receive their signals from more than one satellite atomic clock. This figure is then automatically averaged for the most accurate time.

One of the first radio clocks was put out by Heath Company in 1983.  It was called the GC-1000. This model was considered to be very accurate because it was able to locate and receive the strongest radio signals even when radio propagation was compromised. 

For example, during inclement weather conditions it could still pick up and receive time transmissions. The GC-1000 initially sold for $250 (in a kit that required assembly) and $400 (already fully assembled).  Around 2000, radio-based "atomic clocks" became common in retail electronic stores.  Most were priced between $20-$50.

Stores might sell radio clocks as atomic clocks, but the clocks are not really atomic. For example, radio clocks actually receive time signals from a radio station. The radio station receives its time from an atomic clock.

To set up an atomic clock at home and get the best possible time reception, the clock should be placed near a window.  This will allow it to receive radio transmissions.  The path to the transmitter needs to be clear or unblocked for the clock to work properly and keep accurate time.

The clock will synchronize itself once a day and once at night. It will also need good weather conditions in order to update the time successfully. Overall, radio clocks are an inexpensive way for almost anyone to access and keep accurate time over a broad area via radio or satellite transmissions.