BPM (time service)

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BPM is the call sign of the official short-wave time signal service of the People's Republic of China, operated by the Chinese Academy of Sciences, broadcasting from CAS's National Time Service Center in Pucheng County, Shaanxi at 34°56′55.96″N 109°32′34.93″E / 34.9488778°N 109.5430361°E / 34.9488778; 109.5430361Coordinates: 34°56′55.96″N 109°32′34.93″E / 34.9488778°N 109.5430361°E / 34.9488778; 109.5430361, roughly 70 km northeast of Lintong,[1] along with NTSC's long-wave time signal BPL on 100 kHz.

BPM is broadcast at 2.5, 5.0, 10.0, and 15.0 MHz, the same frequencies as WWV and WWVH, following the schedule listed below:[2]

MHz UTC CST
2.5 7:30-1:00 15:30-9:00
5 0:00-24:00 0:00-24:00
10 0:00-24:00 0:00-24:00
15 1:00-9:00 9:00-17:00

Transmission format[edit]

BPM transmits different signals on a half-hour schedule, modulated with 1 kHz audio tones to provide second and minute ticks:

BPM transmission schedule[2][3]
Minute Duration Transmission
00 30 10 UTC: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms.[4]
BCD time code on 125 Hz sub-carrier.[5]
10 40 5 Carrier (no time code)
15 45 10 UTC: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms.[4]
BCD time code on 125 Hz sub-carrier.[5]
25 55 4 UT1: 100 ms second ticks, 300 ms minute ticks.
29 59 1 Station identification: Morse call sign for 40 seconds, then voice announcement "BPM 标准时间标准频率发播台" ("BPM standard time, standard frequency transmission station") twice for 20 seconds.

BPM is idiosyncratic in that it transmits UT1 time between minutes 25 through to 29 and 55 through to 59, which creates an odd click-beep effect when heard below a stronger time signal station such as WWV especially when UT1 seconds are halfway between UTC seconds, close to a leap-second event.[6]

BPM time code[5]
Bit Weight Meaning Ex Bit Weight Meaning Ex Bit Weight Meaning Ex
:00 No 125 Hz (minute mark) :20 1 Day of month
Example: 28
0 :40 1 Year
Example: 06
0
:01 1 Minutes
Example: 23
1 :21 2 0 :41 2 1
:02 2 1 :22 4 0 :42 4 1
:03 4 0 :23 8 1 :43 8 0
:04 8 0 :24 0 0 :44 0 0
:05 0 0 :25 10 0 :45 10 0
:06 10 0 :26 20 1 :46 20 0
:07 20 1 :27 0 Reserved, always 0. 0 :47 40 0
:08 40 0 :28 0 0 :48 80 0
:09 P1 Marker M :29 P3 Marker M :49 P5 Marker M
:10 1 Hours
Example: 19
1 :30 1 Month
Example: 02
0 :50 + DUT1 sign (1=positive) 1
:11 2 0 :31 2 1 :51 0.1 DUT1 magnitude (0 to 0.9 s)
DUT1 = UT1−UTC
Example: +0.5 s
1
:12 4 0 :32 4 0 :52 0.2 0
:13 8 1 :33 8 0 :53 0.4 1
:14 0 0 :34 0 0 :54 0.8 0
:15 10 1 :35 10 0 :55 0 Reserved, always 0. 0
:16 20 0 :36 0 Reserved, always 0. 0 :56 0 0
:17 0 Reserved, always 0. 0 :37 0 0 :57 LS Leap second 0
:18 0 0 :38 0 0 :58 0 Reserved, always 0. 0
:19 P2 Marker M :39 P4 Marker M :59 P0 Marker M

References[edit]

  1. ^ "National Time Service Center: Facilities". 
  2. ^ a b "短波授时台". National Time Service Center. Archived from the original on 2015-04-10. 
  3. ^ Marco1971 (2007-01-23). "Re: A question about Wave Ceptor frequency reception". Retrieved 2011-04-29. 
  4. ^ a b BIPM Annual Report on Time Activities – Time Signals, retrieved 2011 September 12.
  5. ^ a b c Dissemination scheme of BPM shortwave time code time-service (in chinese), retrieved 2018 August 20.
  6. ^ "HF (SW) Radio - Time NZ & A". 

External links[edit]