|
|
Decoding The MSF-60 UK Radio Time Broadcast
The MSF time and frequency broadcast is a radio time signal transmitted from Anthorn, Cumbria in the UK. The signal can be used as an accurate and reliable source of time derived from atomic clocks at the UK National Physics Laboratory. The effective radiated power of the transmitter is 15kW, providing a transmission range of approximately 1000 km. The signal can be received throughout the UK and much of northwestern Europe. It is often used by synchronised clocks and watches and network time servers. This article describes how the MSF-60 time broadcast is transmitted and can be decoded by computer systems to provide an accurate timing reference.
The MSF radio signal is maintained by VT communications under contract from the National Physics Laboratory (NPL). The broadcast is monitored by NPL and adjusted as necessary to maintain accuracy. When decoded, the MSF-60 time signal provides a highly accurate and reliable timing reference for clocks, NTP Time Servers and other computer timing equipment.
Signal reception problems can generally be attributed to local environmental conditions. The radio signal can be blocked or weakened by metal structures or frames, which effectively act as a Faraday cage. Additionally, signal reception can be difficult near electrically noisy equipment. Radio receivers should also be located above ground, reception underground or in basements can prove difficult. The transmission is taken off-air once or twice a year for short durations for maintenance work on the transmitter. A list of scheduled outages is available from the NPL website.
Time and date information is transmitted continuously, repeated each minute. The data is transmitted as on-off carrier modulated, pulse-width coded data signal. Each data bit is transmitted as a pulse, one per second. The data transmitted consists of the current time and date, leap second indicator, daylight saving time indicator and parity bits.
A 500-millisecond carrier off period indicates the start of each minute. The other 59 seconds consist of between 100 and 300 milliseconds carrier off and at least 700 milliseconds of carrier on. Time and date information is presented in BCD (Binary Coded Decimal) format and is encoded as follows: bits 1-16 are used to convey information about the difference between atomic and astronomical time (DUT1).
The remaining bits, 17 to 59, contain date and time information about the current minute as follows: bits 17-24, BCD encoded year (00-99); bits 25-29, BCD month of year (01-12); bits 30-35, BCD encoded day of month (01-31); bits 36-38, BCD encoded day of week (0-6, 0 = Sunday); bits 39-44, BCD encoded hour (00-23); bits 45-51, BCD encoded minute (00-59).
During British Summer Time, bit 58 is set to '1'. Also in the 60 minutes leading up to a change in British Summer Time, bit 53 is set to '1'.
To summarise, the MSF radio time and frequency broadcast provides a reliable and accurate source of time for radio-controlled clocks, computer network timing equipment and many other applications. It can be received throughout the UK, and with relatively low-cost radio receivers provides a precise, traceable time reference.
About the Author David Evans is a technical author in the field of time and frequency applications. Click here to find out more about network time server solutions.
|
 |
Please Rate: |
|
Rating: |
 Processing ... |
(Average: Not rated) |
| Views: | 31 | |
|
| More Articles from Science | | |
| Top Articles in Science | | |
|
