View source for BPM (time service)

{{Short description|People's Republic of China time signal}}
[[File:Bpm time signal.png|alt=|thumb|319x319px|BPM time signal in waterfall]]
'''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 {{Coord| 34|56|55.96|N|109|32|34.93|E|type:landmark_region:CN-61|display=it}}, roughly 70&nbsp;km northeast of [[Lintong District|Lintong]],<ref>{{cite web
  | url = http://english.ntsc.cas.cn/rs/fs/200909/t20090917_39104.html
  | title = National Time Service Center: Facilities
}}</ref> along with NTSC's long-wave time signal [[BPL (time service)|BPL]] on 100&nbsp;kHz.

BPM is broadcast at 2.5, 5.0, 10.0, and 15.0 [[Megahertz|MHz]], the same frequencies as [[WWV (radio station)|WWV]] and [[WWVH]], following the schedule listed below:<ref name=ntsc>{{cite web
 |title=短波授时台 
 |url=http://www.time.ac.cn/center/222.html 
 |website=National Time Service Center 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20150410130817/http://www.time.ac.cn/center/222.html 
 |archive-date=2015-04-10 
}}</ref>
{| class="wikitable"
|-
! MHz !! [[UTC]] !! [[China Standard Time|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 ==
{{Listen|filename=Bpm_cut.ogg|title=Sample of BPM time signal|description=The BPM time signal, recorded at 2007-01-07 in Beijing, {{Duration|m=5|s=21}}}}
{{Listen|filename=BPM_5_MHz_record,_start_at_21-07-58_18_Jul_2018.ogg|title=BPM time signal with 125 Hz sub-carrier|description=The BPM time signal, recorded at 2018-07-18 on WebSDR from Netherlands, {{Duration|m=1|s=4}}}}{{Listen
| filename     = Bpmtm.wav
| title        = BPM time signal with 100 Hz sub-carrier
| description  = The BPM time signal, recorded at 2023-10-13 on KiwiSDR from Japan, 18:07
}}
{{Listen
| filename     = 
| title        = 
}}

BPM transmits different signals on a half-hour schedule, modulated with 1&nbsp;kHz audio tones to provide second and minute ticks:
{|style="text-align:center" class="wikitable"
|+BPM transmission schedule<ref name=ntsc /><ref>{{cite web
  | url = http://forums.watchuseek.com/f17/question-about-wave-ceptor-frequency-reception-46487.html#post258489
  | title = Re: A question about Wave Ceptor frequency reception
  | author = Marco1971
  | date = 2007-01-23
  | access-date = 2011-04-29
}}</ref>
! colspan=2 | Minute !! Duration !! Transmission
|-
| 00 || 30 || 10 || align=left | [[UTC]]: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms.<ref name="BIPM">BIPM Annual Report on Time Activities &ndash; [https://web.archive.org/web/20211010023818/ftp://ftp2.bipm.org/pub/tai/scale/TIMESIGNALS/timesignals.pdf Time Signals], retrieved 2011 September 12.</ref><br />[[Binary-coded decimal|BCD]] time code on 100&nbsp;Hz sub-carrier.<ref name="tc">[https://bbs.pku.edu.cn/attach/fc/ac/fcac420edd48d7bd/BPM%E7%9F%AD%E6%B3%A2%E6%97%B6%E7%A0%81%E6%8E%88%E6%97%B6%E5%8F%91%E6%92%AD%E6%8A%80%E6%9C%AF%E6%96%B9%E6%A1%88_%E8%92%99%E6%99%BA%E8%B0%8B.pdf Dissemination scheme of BPM shortwave time code time-service] (in chinese), retrieved 2018 August 20.</ref>
|-
| 10 || 40 ||  5 || align=left | Carrier (no time code)
|-
| 15 || 45 || 10 || align=left | UTC: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms.<ref name="BIPM"/><br />BCD time code on 100&nbsp;Hz sub-carrier.<ref name="tc"/>
|-
| 25 || 55 ||  4 || align=left | [[UT1]]: 100 ms second ticks, 300 ms minute ticks.
|-
| 29 || 59 ||  1 || align=left | 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 (radio station)|WWV]] especially when UT1 seconds are halfway between UTC seconds, close to a leap-second event.<ref>{{cite web
 |url          = http://tufi.alphalink.com.au/time/time_hf.html
 |title        = HF (SW) Radio - Time NZ & A
 |access-date  = 2011-04-25
 |archive-url  = https://archive.today/20121230125806/http://tufi.alphalink.com.au/time/time_hf.html
 |archive-date = 2012-12-30
 |url-status     = dead
}}</ref>

{|class=wikitable style="text-align:center;"
|+ BPM time code<ref name="tc"/>
! Bit || Weight || Meaning || Ex
|rowspan=21|
! Bit || Weight || Meaning || Ex
|rowspan=21|
! Bit || Weight || Meaning || Ex
|- 
|bgcolor=lightblue| :00 ||bgcolor=lightblue colspan=3| No 125&nbsp;Hz (minute mark)
| :20 || 1 ||rowspan=7 | Day of month<br />''Example: 28'' || 0
| :40 || 1 ||rowspan=9| Year<br />''Example: 06'' || 0
|- 
| :01 || 1 ||rowspan=8| Minutes<br />''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
|bgcolor=lightgrey| :24 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
|bgcolor=lightgrey| :44 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
|-
|bgcolor=lightgrey| :05 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
| :25 || 10 || 0
| :45 || 10 || 0
|-
| :06 || 10 || 0
| :26 || 20 || 1
| :46 || 20 || 0
|-
| :07 || 20 || 1
|bgcolor=lightgrey| :27 ||bgcolor=lightgrey| 0 ||rowspan=2 bgcolor=lightgrey| ''Reserved, always 0.'' ||bgcolor=lightgrey| 0 
| :47 || 40 || 0
|-
| :08 || 40 || 0 
|bgcolor=lightgrey| :28 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0 
| :48 || 80 || 0
|- bgcolor=lightpink
| :09 || P1 || Marker || M
| :29 || P3 || Marker || M
| :49 || P5 || Marker || M
|-
| :10 || 1 ||rowspan=7| Hours<br />''Example: 19'' || 1
| :30 || 1 ||rowspan=6 | Month<br />''Example: 02'' || 0
| :50 || + || [[DUT1]] sign (1=positive) || 1
|-
| :11 || 2 || 0
| :31 || 2 || 1
| :51 || 0.1 ||rowspan=4| DUT1 magnitude (0 to 0.9 s)<br />DUT1 = [[UT1]]−UTC<br />''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
|- 
|bgcolor=lightgrey| :14 ||bgcolor=lightgrey| 0 || bgcolor=lightgrey| 0
|bgcolor=lightgrey| :34 ||bgcolor=lightgrey| 0 || bgcolor=lightgrey| 0
| :54 || 0.8 || 0
|-
| :15 || 10 || 1
| :35 || 10 || 0
|bgcolor=lightgrey| :55 ||bgcolor=lightgrey| 0 ||rowspan=2 bgcolor=lightgrey| ''Reserved, always 0.'' ||bgcolor=lightgrey| 0
|-
| :16 || 20 || 0
|bgcolor=lightgrey| :36 ||bgcolor=lightgrey| 0 ||rowspan=3 bgcolor=lightgrey| ''Reserved, always 0.'' ||bgcolor=lightgrey| 0
|bgcolor=lightgrey| :56 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
|-
|bgcolor=lightgrey| :17 ||bgcolor=lightgrey| 0 ||rowspan=2 bgcolor=lightgrey| ''Reserved, always 0.'' ||bgcolor=lightgrey| 0 
|bgcolor=lightgrey| :37 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
| :57 || LS || Leap second || 0
|- 
|bgcolor=lightgrey| :18 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
|bgcolor=lightgrey| :38 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| 0
|bgcolor=lightgrey| :58 ||bgcolor=lightgrey| 0 ||bgcolor=lightgrey| ''Reserved, always 0.'' ||bgcolor=lightgrey| 0
|- bgcolor=lightpink
| :19 || P2 || Marker || M
| :39 || P4 || Marker || M
| :59 || P0 || Marker || M
|}

== References ==
{{reflist}}

== External links ==
* {{YouTube|id=yuQPjgK6hjc|title=Recorded video of the broadcast BPM time signal}}
* [http://english.ntsc.cas.cn National Time Service Center]
* [https://web.archive.org/web/20150410130817/http://www.time.ac.cn/center/222.html 短波授时台(Shortwave time signal station)], from the National Time Service Center, Chinese Academy of Sciences https://www.sigidwiki.com/wiki/BPM
{{Time signal stations}}
{{Time signal authorities}}

{{DEFAULTSORT:Bpm (Time Service)}}
[[Category:Time signal radio stations]]
[[Category:Radio stations in China]]
[[Category:Shortwave radio stations]]


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