Radio Controlled Clocks

There are three types of radio controlled clocks/watches.
  1. Radio controlled clock pre-set to a specific country i.e. pre-tuned to a specific frequency. Will only receive the time signal from the transmitter in that country.
  2. Radio controlled clock with automatic tuning. Will receive signal from nearest transmitter. May cause problems if used in a zone between two transmitters where it sometimes picks up one signal (e.g. UK) and sometimes another (e.g. Germany)
  3. Global radio controlled clock with a user setting. A slider switch (or some other type of control) permits the user to choose which frequency (transmitter) the clock will use.
A clock or watch that's been able to sync to a radio signal from a transmitter will continue to operate when it's out of range of a signal, it just won't be able to update itself, so will slowly lose its accuracy until it's able to get a signal again.

How to Choose the Right Radio Controlled Clock

If you intend to use the clock in one country only, for example in your home, then the best choice is a clock pre-tuned to the transmitter nearest your location. There are four main transmitters located in the UK, Europe (Germany), USA and Japan. This type of clock is factory set to the best transmitter for your location and cannot be changed. If you later decide to relocate from, for example, the UK to the USA, then your clock will only function as an ordinary clock in the new location, it will not pick up the UK signal in the USA because it is out of range and it will not be able to sync to the US radio signal because it is on a different frequency.

In most cases pre-tuned radio controlled clocks sold in the UK are pre-tuned to the UK transmitter, radio controlled clocks sold in the USA are pre-tuned to the USA transmitter, radio controlled clocks sold in Europe are pre-tuned to the European transmitter (located in Germany) and radio controlled clocks sold in Japan are pre-tuned to the Japanese transmitter. If you buy a radio controlled clock abroad, for example on holiday, or from a website, you need to check which frequency the clock uses.

Some radio controlled clocks are built with automatic tuning. This means that they will automatically seek the nearest (strongest) radio signal and sync the time to that signal. The advantage is that you can buy this sort of radio controlled clock anywhere in the world and use it in the UK, Europe etc and if you relocate to, for example, Japan or the US, the clock will still function as a radio controlled clock. Beware of one important problem with this type of radio controlled clock. If you use it in an area between two zones, for example on the east coast of England or in northern France where it is possible to pick up both the UK and the German signal, your clock will sync with the strongest signal. Depending on atmospheric conditions and other factors the relative signal strengths may vary. So you may go to bed with your clock on UK time and wake up not realising that during the night it reset itself to European time (one hour different).

If you want to use your radio controlled clock in different countries, for example if you want a radio controlled travel alarm clock, then you really need a global radio controlled clock with a user setting that allows you to choose the appropriate radio signal, or to put it another way, it permits the user to select the frequency. The choice is usually: UK, USA, Europe (Germany), or Japan. You need to adjust the controller when you arrive in the new location and allow the clock to reset itself to the appropriate time.