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Time and frequency

Time and frequency GPS bulletins

Monitoring and ensuring accurate time

The NPL Monthly Bulletins for time and frequency cover the three standard-frequency and time radio signals that are most widely used in the UK. The signals reported in the Monthly Bulletins are:

  • The MSF 60 kHz standard-frequency and time signal operated by NPL
  • The 198 kHz long-wave transmission from Droitwich radio station
  • The GPS navigation satellite signals

These Bulletins provide both information about the availability of each signal and a means of obtaining traceability between the signals and the UK national time scale, UTC(NPL). A fourth Bulletin gives the offset between UTC(NPL) and the global time standard, Coordinated Universal Time (UTC), as published by the International Bureau of Weights and Measures (BIPM) in its monthly Circular T.

The Bulletins are used in a two-stage process, first relating measurements of each signal back to the UK national time standard, UTC(NPL), and then (if required) correcting the offset between UTC(NPL) and UTC.

How to use the NPL Monthly Bulletins

The User's Guide to the NPL Monthly Bulletins gives more background information about each of the signals and explains how to interpret and make use of the information provided in each of the bulletins.

Access to the NPL Monthly Bulletins

The NPL Monthly Bulletins for time and frequency are free of charge, and are available in two ways:

  1. By email, as PDF attachments.
    Please complete this online subscription form if you would like to receive the bulletins by email each month
  2. The latest bulletins (MSF (60 kHz), Droitwich (198 kHz), GPS and BIPM Circular T Summary) are available for download. 

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