The MSF time signal is a dedicated radio broadcast providing an accurate and reliable source of UK civil time, based on the global time scale UTC (Coordinated Universal Time), the MSF signal is broadcast and maintained by the UK’s National Physical Laboratory (NPL).
The MSF time signal can be utilised by anyone requiring accurate timing information its main use however is as a source of UTC time for administrators synchronising a computer network with a radio clock. Radio clocks are really another term for a network time server that utilises a radio transmission as a timing source.
The MSF signal is broadcast from Anthorn Radio station in Cumbria by VT communications under contract to the NPL. It is available 24 hours a day across the whole of the UK and beyond, although the signal is vulnerable to interference and local topography. Users of the MSF service receive predominantly a ‘ground wave’ signal. However, there is also a residual ‘sky wave’ which is reflected off the ionosphere and is much stronger at night; this can result in a total received signal that is either stronger or weaker.
The MSF signal is carried on a frequency of 60 kHz (to within 2 parts in 1012) and is controlled by a Caesium atomic clock based at the radio station.
The antenna at Anthorn is at 54° 55′ N latitude, and 3° 15′ W longitude. The signal’s field strength exceeds 100 µV/m(micro volts a metre) at a distance of 1000 km from Anthorn, covering the whole of the UK, and can even be received throughout some of northern and western Europe.
The MSF transmits a simple binary code containing time and date information The MSF time and date code includes the following information: year, month, day of month, day of week, hour, minute, British Summer Time (in effect or imminent), DUT1 (a parameter giving UT1-UTC)