National Physical Laboratory

MSF Radio Time Signal

Anthorn Signal Coverage Map
Anthorn signal coverage map

The MSF radio signal is a dedicated time broadcast that provides an accurate and reliable source of UK civil time, based on the NPL time scale UTC(NPL). It is available 24 hours a day across the whole of the UK and beyond. The signal operates on a frequency of 60 kHz and carries a time and date code that can be received and decoded by a wide range of readily available radio-controlled clocks.

The MSF signal is transmitted from Anthorn Radio Station in Cumbria by Babcock (formerly VT Communications), under contract to NPL.

The antenna at Anthorn is at latitude 54° 55' N, and longitude 3° 15' W. The radiated power is typically around 17 kW and the horizontal radiation pattern is substantially omnidirectional. The signal provides a field strength exceeding 100 µV/m at a distance of 1000 km from Anthorn, which covers the whole of the UK, and it can be satisfactorily received throughout much of northern and western Europe.

MSF Antenna
Masthead view of the MSF antenna
(Source: VT Communications)

The signal's carrier frequency is maintained at 60 kHz to within 2 parts in 1012, controlled by caesium atomic clocks at the radio station. The broadcast signal is monitored against the national time standard at the NPL site in Teddington and corrected when necessary, allowing it to be used as a frequency reference. Companies that need traceability from the MSF carrier frequency to UTC(NPL) and UTC can subscribe to the NPL Monthly Bulletins.

MSF Time and Date Code

The MSF signal carries time and date information that is transmitted in a simple binary-coded decimal format by on-off modulation of the carrier. The full sequence of information is transmitted each minute, using two data bits during every second of the minute except the first.

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; see the information sheet link below for more explanation)

MSF Antenna
Base of the MSF antenna
(Source: VT Communications) 

An information sheet is available that describes in details the format of the time and date code (PDF File PDF 80 KB).

Interruptions to the MSF Signal

The MSF signal is taken off-air a few times a year for planned maintenance work on the masts and antenna. A list of the scheduled outages is available.

MSF Reception Difficulties

If your radio-controlled clock is having difficulty receiving the MSF signal, please first read through the information in the Common Clock Problems page.

The main causes of reception problems are local interference from electrical equipment and a reduced local signal due to screening by nearby metalwork, for example in a steel-framed building.

MSF Bulletins

Each month, NPL publishes a series of four monthly time and frequency bulletins. One of these provides daily values for the phase time difference between the MSF 60 kHz carrier and the NPL time scale UTC(NPL). The measurements provide users of the signal a frequency reference with traceability to UTC(NPL).

Last Updated: 7 Feb 2014
Created: 22 Apr 2010