- MSF background -

MSF Decoder Project as featured in RadioUser magazine.

 

The MSF time signal is broadcast at a frequency of 60 kHz and carries the UK's national time reference. The radio signal is transmitted from Anthorn in Cumbria.

 

As well as transmitting the time the MSF signal can be used as a frequency reference as the carrier is maintained at 60 kHz to within 2 parts in 1012.

 

MSF is broadcast by Babcock under contract on behalf of UKs National Physical Laboratory (NPL). The service is controlled by caesium atomic clocks at the transmitting site, accuracy monitored by NPL at Teddington.

 

Time and date code information broadcast by MSF is always given in terms of UK clock time in GMT (Greenwich Mean Time). In winter local time this is GMT, and GMT+1 hour when British Summer Time (BST) is in effect (last Sunday in March to last Sunday in October).

 

The time signal is governed by Coordinated Universal Time (UTC), which is always within a second of GMT. The term UTC is often interchanged with GMT and occasionally UT1 (Universal Time, a more scientifically defined variant of GMT). However from a historical view there are key technical differences between GMT and UTC time standards.

 

 

 

 

second

bit A

bit B

BCD

meaning

0

1

1

 

minute mark

1

0

X

 

+100 mSec DUT1

2

0

X

 

+100 mSec

3

0

X

 

+100 mSec

4

0

X

 

+100 mSec

5

0

X

 

+100 mSec

6

0

X

 

+100 mSec

7

0

X

 

+100 mSec

8

0

X

 

+100 mSec

9

0

X

 

-100 mSec

10

0

X

 

-100 mSec

11

0

X

 

-100 mSec

12

0

X

 

-100 mSec

13

0

X

 

-100 mSec

14

0

X

 

-100 mSec

15

0

X

 

-100 mSec

16

0

X

 

-100 mSec

17

X

0

80

Year (0-99) (MSB)

18

X

0

40

 

19

X

0

20

 

20

X

0

10

 

21

X

0

8

 

22

X

0

4

 

23

X

0

2

 

24

X

0

1

 

25

X

0

10

Month (MSB)

26

X

0

8

 

27

X

0

4

 

28

X

0

2

 

29

X

0

1

 

30

X

0

20

Day of month (MSB)

31

X

0

10

 

32

X

0

8

 

33

X

0

4

 

34

X

0

2

 

35

X

0

1

 

36

X

0

4

Day of the week (MSB)

37

X

0

2

0 = Sunday, 6 = Saturday

38

X

0

1

 

39

X

0

20

Hour (MSB)

40

X

0

10

 

41

X

0

8

 

42

X

0

4

 

43

X

0

2

 

44

X

0

1

 

45

X

0

40

Minute (MSB)

46

X

0

20

 

47

X

0

10

 

48

X

0

8

 

49

X

0

4

 

50

X

0

2

 

51

X

0

1

 

52

0

0

-

always 0

53

1

X

BST/

GMT

BST/GMT change warning

54

1

X

P1

parity year

55

1

X

P2

parity - day of the month

56

1

X

P3

parity - day of week

57

1

X

P4

parity time

58

1

X

BST

0 = GMT, 1 = BST

59

0

0

-

always 0

 

X = transmitted data.

MSB = Most Significant Bit.

 

Summary of data sent for each second

 

MSF background
MSF home
PIC circuit
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