Recommendation itu-r tf. 768-5 Standard frequencies and time signals




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Rec. ITU-R TF.768-5

RECOMMENDATION ITU-R TF.768-5

Standard frequencies and time signals


(1992-1994-1995-1997-2001-2002)

The ITU Radiocommunication Assembly,

considering

a) the continuing need in all parts of the world for readily available standard frequency and time reference signals that are internationally coordinated;

b) the advantages offered by radio broadcasts of standard time and frequency signals in terms of wide coverage, ease and reliability of reception, achievable level of accuracy as received, and the wide availability of relatively inexpensive receiving equipment;

c) that Article 26 of the Radio Regulations (RR) is considering the coordination of the establishment and operation of services of standard-frequency and time-signal dissemination on a worldwide basis;

d) that a number of stations are now regularly emitting standard frequencies and time signals in the bands allocated by the World Administrative Radio Conference (Geneva, 1979) (WARC-79) and that additional stations provide similar services using other frequency bands;

e) that these services operate in accordance with Recommendation ITU-R TF.460 which establishes the internationally coordinated UTC time system;

f) that other broadcasts exist which, although designed primarily for other functions such as navigation or communications, emit highly stabilized carrier frequencies and/or precise time signals that can be very useful in time and frequency applications,

recommends

1 that, for applications requiring stable and accurate time and frequency reference signals that are traceable to the internationally coordinated UTC system, serious consideration be given to the use of one or more of the broadcast services listed and described in Annex 1;

2 that administrations responsible for the various broadcast services included in Annex 2 make every effort to update the information given whenever changes occur. (Administrations are also requested to send such information to the Bureau international des poids et mesures (BIPM).)

ANNEX 1


Characteristics of standard-frequency and time-signal emissions in allocated bands and characteristics of stations emitting with regular schedules with
stabilized frequencies, outside of allocated bands


1 The characteristics of stations are contained in Tables 1, 2 and 3. For information concerning changes which may have occurred since the date when this Recommendation was approved, reference may be made to the Annual Report of the time section of the BIPM or directly to the respective authority for each service as listed in Annex 2.

TABLE 1


Characteristics of standard-frequency and time-signal emissions in the allocated bands


Station

Type of antenna(s)

Carrier power
(kW)


Number of simulta-
neous trans-missions


Period of
operation


Standard
frequencies used


Duration of emission

Uncertainty
of frequency
and time intervals
(parts in 1012(1)


Method of
DUT1
indication


Call sign

Approximate location

Latitude Longitude

Days/
week


Hours/
day


Carrier
(MHz)


Modu-lation
(Hz)


Time signal
(min)


Audio-modulation
(min)


ATA

New Delhi,
India

28 34 N
77 19 E

Horizontal folded
dipole

8 (PEP)

3

7

24 (2)

5,
10,
15

1, 1 000

Continuous

4/15

 10




BPM(3)

Pucheng,
China

35 00 N
109 31 E

Omni-directional

10-20

2

7

24 (4)

2.5,
5,
10,
15

1, 1 000

20/30
(UTC)
4/30 (UT1)

Nil

 10

Direct emission of UT1 time signal

HLA

Taejon,
Taedok
Science Town,
Republic
of Korea

36 23 N
127 22 E

Vertical (conical monopole)

2

1

5 (5)

7 (6)

5

1

Continuous

Continuous

 10

ITU-R code by double pulse

IAM(7)

Rome,
Italy

41 47 N
12 27 E

Vertical /4

1

1

6

2

5

1

Continuous

Nil

 10

ITU-R code by double pulse

JJY(7)

Sanwa,
Sashima, Ibaraki, Japan

36 11 N
139 51 E

 (8)

2

3

7

24 (9)

5,
8,
10

1 (10),
1 000 (11)

Continuous

30/60

 10

ITU-R code by lengthening

LOL(7)

Buenos Aires,
Argentina

34 37 N
58 21 E

Horizontal
3-wire
folded dipole

2

3

7

5

5,
10,
15

1,
440,
1 000

Continuous

3/5

 20

ITU-R code by lengthening

OMA(7)

Prague, Czech
Republic

50 07 N
14 35 E

T

1

1

7

24

2.5

1,
1 000 (12)

15/30

4/15

 1 000




TABLE 1 (end)


Station

Type of antenna(s)

Carrier power
(kW)


Number of simulta-
neous trans-missions


Period of
operation


Standard
frequencies used


Duration of emission

Uncertainty
of frequency
and time intervals
(parts in 1012(1)


Method of
DUT1
indication


Call sign

Approximate location

Latitude Longitude

Days/
week


Hours/
day


Carrier
(MHz)


Modu-lation
(Hz)


Time signal
(min)


Audio-modulation
(min)


RWM(7)

Moscow

55 44 N
38 12 E

Horizontal dipole

5
5
8

3

7

24

4.996,
9.996,
14.996

1/60, 1, 10

40/60

Nil

 10

ITU-R code by double pulse, additional
information dUT1 (13)

VNG

Llandilo,
New South Wales,
Australia

33 43 S
150 48 E

Omni-
directional

10
1

2

7

24

5,
2.5

1,
1 000 (14)

Continuous

Nil

 100

ITU-R code by 45 cycles of 900 Hz immediately following the normal second markers

WWV(7)

Fort Collins,
Colorado,
United States

40 41 N
105 02 W

Vertical
/2
dipoles

2.5-10

5

7

24

2.5,
5,
10,
15, 20 (15)

1,
440, 500, 600

Continuous
(16)

Continuous (17)

 10

ITU-R code by double pulse, additional information on UT1 corrections

WWVH(7)

Kekaha,
Kauai, Hawaii,
United States

21 59 N
159 46 W

Vertical
/2
dipole
arrays

2.5-10

4

7

24

2.5,
5,
10,
15 (15)

1,
440, 500, 600

Continuous (16)

Continuous (17)

 10

ITU-R code by double pulse, additional information on UT1 corrections




Notes to Table 1:

The daily transmission schedule and hourly modulation schedule is given, where appropriate, in the form of Figs. 1 and 2 supplemented by the following Notes:



(1) This value applies at the transmitter; to realize the quoted uncertainty at the point of reception it could be necessary to observe the received phase time frequency over a sufficiently long period in order to eliminate noise and random effects.

(2) 5 MHz: 1800-0900 h UTC; 10 MHz: 24 h; 15 MHz: 0900-1800 h UTC.

(3) Call sign in Morse and language.

(4) 2.5 MHz: 0730-0100 h UTC; 15 MHz: 0100-0900 h UTC; 5 MHz and 10 MHz: continuous.

(5) Monday to Friday (except national holidays in Korea).

(6) 0100 to 0800 h UTC. Pulses of 9 cycles of 1 800 Hz modulation. 59th and 29th second pulses omitted. Hour identified by 0.8 s long 1 500 Hz tone. Beginning of each minute, identified by a 0.8 s long 1 800 Hz tone, voice announcement of hours and minutes each minute following 52nd second pulse. BCD time code given on 100 Hz sub-carrier.

(7) These stations have indicated that they follow the UTC system as specified in Recommendation ITU-R TF.460. Since 1 January 1972 the frequency offset has been eliminated and the time signals remain within about 0.8 s of UT1 by means of occasional 1 s steps as directed by the International Earth Rotation Service.

(8) Horizontal /2 dipole for 5 and 8 MHz, and vertical /2 dipoles for 10 MHz.

(9) Interrupted from 35 to 39 min of each hour.

(10) Pulse consists of 8 cycles of 1 600 Hz tone. First pulse of each minute preceded by 655 ms of 600 Hz tone.

(11) 1 000 Hz tone modulation between the minutes of 0-5, 10-15, 20-25, 30-35, 40-45, 50-55 except 40 ms before and after each second’s pulse.

(12) In the period from 1800-0600 h UTC, audio-frequency modulation is replaced by time signals.

(13) The additional information about the value of the difference UT1 – UTC is transmitted by code dUT1. It provides more precisely the difference UT1 – UTC in multiples of 0.02 s. The total value of the correction is DUT1  dUT1. Possible values of dUT1 are transmitted by marking of p second pulses between the 21st and 24th seconds of the minute, so that dUT1   0.02 s  p. Negative values of dUT1 are transmitted by marking of q second pulses between the 31st and 34th second of the minute, so that dUT1  –0.02 s  q.

(14) Pulses of 50 cycles of 1 000 Hz tone, shortened to 5 cycles from the 55th to the 58th second; the 59th pulse is omitted; the minute marker is 500 cycles. At the 5th, 10th, 15th, etc. minutes, pulses from the 50th to the 58th second are shortened to 5 cycles. Voice identification on 5 000 kHz between the 20th and 50th seconds in the 15th, 30th, 45th and 60th min. A BCD time incorporating time of day and day number of the year is transmitted between the 20th and 46th second with a binary “0” represented by 100 cycles and a binary “1” by 200 cycles of 1 000 Hz tone. The minute information for the next minute is given from the 21st to the 28th second, hour information from the 29th to the 35th second and day of the year from the 36th to the 46th second; parity bits are included at the end of each code sequence.

(15) As of 1 February 1977 transmissions on 25 MHz from WWV and 20 MHz from WWVH were discontinued, but may be resumed at a later date.

(16) In addition to other timing signals and time announcements, a modified IRIG-H time code is produced at a 1-pps rate and radiated continuously on a 100 Hz sub carrier on all frequencies. A complete code frame is 1 min. The 100 Hz sub-carrier is synchronous with the code pulses, so that 10 ms resolution is obtained. The code contains DUT1 values; UTC time expressed in year, day of year, hour and minute; and status indicators relating to impending leap seconds and Daylight Saving Time.

(17) Except for voice announcement periods and the 5 min semi-silent period each hour.






Notes to Fig. 1:

Note 1 – Pulse of 5 cycles of 1 000 Hz (WWV) or 6 cycles of 1 200 Hz (WWVH) tone, lengthened to 0.8 s at the beginning of each minute. An 0.8 s pulse of 1 500 Hz begins each hour at both stations. 29th and 59th pulses each minute are omitted. Voice time announcements preceding each minute. 45 s audio tones alternating between 500 and 600 Hz each minute, except when special announcements or station identification messages are given in voice. One 45 s segment of 440 Hz is included each hour at 1 min (WWVH) or 2 min (WWV) past the hour. A modified IRIG-H time code, giving the year, day of year, hour, minute, DUT1 value, and information on impending leap seconds and Daylight Saving Time, is broadcast continuously on a 100 Hz sub carrier. DUT1 information is provided by the number and position of doubled second pulses each minute. All modulations interrupted for 40 ms around each second’s pulse.

Note 2 – Voice station identification is provided on the 2 500 kHz, 5 000 kHz and 16 000 kHz frequencies during 15, 30, 45 and 60 minutes without interruption to the time signals. Voice announcement is notched to allow seconds markers to continue, and has the 1 000 Hz components removed.

Morse identification is provided on 8 638 kHz and 12 984 kHz frequencies during the 15, 30, 45 and 60 minutes without interruption to the time signals. VNG is transmitted in slow Morse at a frequency of approximately 400 Hz up to six times per minute. Broken idents may occur at the beginning and end of the minute.

Seconds markers are normally 50 ms of 1 000 Hz, second markers 55 to 58 are 5 ms of 1 000 Hz, second marker 59 is omitted. Minute marker is 500 ms of 1 000 Hz, during 5, 10, 15, etc. minutes, seconds markers 50 to 58 are 5 ms of 1 000 Hz.

DUT1 transmission is from 1 to 16 s after the minute. During this time, normal seconds markers are emphasized by 50 ms of 900 Hz tone. Tone immediately follows.

Seconds marker at 20 s, has 200 ms duration and designates start of the time code information. BCD time code giving year, hour and minute at the next minute, is given between seconds 20 and 46.

TABLE 2


Characteristics of standard-frequency and time-signal emissions in additional bands


Station

Type of antenna(s)

Carrier power
(kW)


Number of simulta-
neous trans-missions


Period of
operation


Standard
frequencies used


Duration of emission

Uncertainty
of frequency
and time intervals
(parts in 1012(1)


Method of DUT1
indication


Call sign

Approximate location

Latitude Longitude

Days/
week


Hours/
day


Carrier
(kHz)


Modu-lation
(Hz)


Time signal
(min)


Audio-modulation
(min)





Allouis,
France

47 10 N
02 12 E

Omni-
directional

1 000
to
2 000

1

7

24

162

1 (2)

Continuous

A3E
broadcast continuously

 2

No DUT1 transmission

CHU(3)

Ottawa,
Canada

45 18 N
75 45 W

Omni-
directional

3, 10, 3

3

7

24

3 330,
7 335,
14 670

1 (4)

Continuous

Nil

 5

ITU-R code by split pulses




Donebach,
F.R. of
Germany

49 34 N
09 11 E

Omni-
directional

250

1

7

24

153

Nil

Nil

A3E
broadcast continuously

 2




DCF77(3)

Mainflingen,
F.R. of
Germany

50 01 N
09 00 E

Omni-
directional

30 (5)

1

7

24

77.5

1

Continuous (6)

Continuous (7)

 0.5

No DUT1 transmission




Droitwich,
United
Kingdom

52 16 N
02 09 W

T

400

1

7

22

198 (8)

Nil

Nil

A3E
broadcast continuously

 20







Westerglen,
United
Kingdom

55 58 N
03 50 W

T

50

1

7

22

198 (8)

Nil

Nil

A3E
broadcast continuously

 20







Burghead,
United
Kingdom

57 42 N
03 28 W

T

50

1

7

22

198 (8)

Nil

Nil

A3E
broadcast continuously

 20




HBG(9)

Prangins,
Switzerland

46 24 N
06 15 E

Omni-
directional

20

1

7

24

75

1 (10)

Continuous

Nil

 1

No DUT1 transmission
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