Guide to Radio Controlled Clocks

The UK broadcasts a MSF time signal from an atomic clock near Anthorn (relocated from Rugby in 2007) with a time deviation of less than one second in one million years. The clock receives the time signal transmitted and then sets its self to the correct local time.

The clock is a radio device similar to a mobile phone or radio. In certain locations and certain times of the day strong radio noise interference often makes synchronisation impossible. Some clocks do not have a manual setting and you just have to wait for it to set.

A strong signal is usually found by a window. In some areas where the signal is poor you may need to position and rotate the clock until the best signal strength is obtained. If the clock is too close to a electrical appliances like a TV, computer or mobile phone they may cause undesirable interference. Topographical and meteorological conditions can have an adverse effect on reception as well as metal clad buildings.

Note: the transmitter is occasionally shut down for scheduled maintenance (dates can be found here. The clock will continue working during this period and any errors will be corrected when the time signal is restored.

General instructions

On analogue clocks the hands will automatically rotate to 4, 8, 12 o'clock position and then 3-5 minutes after receiving the time signal the clock will automatically set to the correct time. If the clock is unable to achieve successful reception the hands will remain at 4, 8 or 12 o'clock and attempt again after two hours. If this happens try moving the clock to a different location, remove the battery for at least a minute and then replace it.

If you are having trouble setting the clock leave it over night by a window with the battery inserted as the signal strength usually improves at night.

The National Institute of Standards and Technology(NIST) broadcasts the time signal in America and various other countries have their own transmitters. A clock usually only works with one transmitter, there is normally a switch to select different transmitters if it can work in more than one location.

To find out more information about radio clocks try: