Clock receivers

Many manufacturers and retailers sell radio clocks under the name "atomic clocks", but the clocks themselves are not atomic. Instead, they receive coded time signals from a radio station, which, in turn, derives the time from a true atomic clock.

One of the first radio clocks was offered by Heathkit in late 1983. Their model GC-1000 "Most Accurate Clock" received shortwave time signals from radio station WWV in Colorado, USA whenever propagation conditions permitted, automatically switching between the 5, 10, and 15 MHz frequencies to find the strongest signal as conditions changed through the day and year. It kept time during periods of poor reception with a quartz-crystal oscillator. This oscillator was disciplined, meaning that the microprocessor-based clock used the highly accurate frequency standard signal received from WWV to trim the crystal oscillator. The timekeeping between updates was thus considerably more accurate than the crystal alone could have achieved. Time down to the tenth of a second was shown on an LED display. The GC-1000 originally sold for US$250 in kit form, US$400 preassembled, and was considered impressive at the time. Heath Company was granted a patent for their design. [2] [3]

In the 2000s radio-based "atomic clocks" became common in retail stores; As of 2010[update] prices start at around US$15 in many countries[citation needed]. Clocks may have other features such as indoor thermometers and weather station functionality. These use signals transmitted by the appropriate transmitter for the country in which they are to be used. Depending upon signal strength they may require placement in a location with a relatively unobstructed path to the transmitter and need fair to good atmospheric conditions to successfully update the time. Inexpensive clocks keep track of the time between updates, or in their absence, with a non-disciplined quartz-crystal clock of similar accuracy to a non-radio-controlled quartz timepiece. Some clocks include an indicator to alert users to possible inaccuracy when synchronization has not been successful within the last 24 to 48 hours. In other cases, the indicator will indicate that synchronization has been achieved within the last few hours, and will go blank in the mid-morning.[citation needed]

Modern radio clocks can be referenced to atomic clocks, and provide access to high-quality atomic-derived time over a wide area using inexpensive equipment. They are suitable for scientific or other work which does not require higher accuracy than they can provide.

Sangean RCR-2 Clock Radio

DESC: The Sangean RCR-2 AM FM Radio has a host of innovative features not found on most clock radios. This stylish radio has two alarms as well as a sleep and nap timer. Since its atomic, youll never have to worry about setting the time or date again. Wake to your favorite radio shows on time, everyday, and never miss a beat.