BPC is the callsign of a time signal broadcasting from the BPC Shangqiu Low-Frequency Time-Code Radio Station, cooperatively constructed by the National Time Service Center of the Chinese Academy of Sciences and Xi'an Gaohua Technology Co., Ltd., beginning April 25, 2002.

BPC transmits a time signal on 68.5 kHz, which can be used for synchronizing radio controlled clocks. The transmission site is situated near Shangqiu, Henan Province[1] at 34°27′25″N 115°50′13″E / 34.457°N 115.837°E / 34.457; 115.837.[2]

BPC broadcasts at 90 kW for 20 hours per day, with a 4-hour break from 05:00–09:00 China Standard Time daily (21:00–1:00 UTC).[3] BPC includes both conventional amplitude modulated time code and additional spread-spectrum time code, about which little is known.[4]

Time code

BPC transmits the time every 20 seconds, using an amplitude-modulated binary code sent at 2 bits per second.

To encode each pair of bits, the transmitter is reduced by 10 dB (to 10% of normal power) at the beginning of each second, and restored to full power after a multiple of 0.1 seconds. The duration of the reduction encodes the bits, as follows:

BPC bit coding
Signal reduced at the beginning of each second
DurationMSbitLSbit
0 msStart of time code
100 ms00
200 ms01
300 ms10
400 ms11

If there is no signal reduction at all, that is a special marker which marks the beginning of the time code.

BPC time code,[5] sent every 20 seconds
SecondMSbit
LSbit		Meaning SecondMSbit
LSbit		Meaning
00—Start of time code
No signal gap		 1012
P1		Hour (0=AM 1=PM)
Even parity over 01–09
0140
20		Second (00, 20 or 40) 110Unused
16Day of month (01–31)
020
0		Unused 128
4
038
4		Hour (00–11)132
1
042
1		148
4		Month (01–12)
0532
16		Minute (00–59)152
1
068
4		1632
16		Year (00–99)
072
1		178
4
080Unused 182
1
4Day of week
1=Monday
7=Sunday
092
1		1964
P2Even parity over 11–18

Note that the bits sent in the same second as the parity bits are not parity-checked.

References

  1. ↑ "Low-frequency radio time signals". Cl.cam.ac.uk. Retrieved 2011-10-20.
  2. ↑ "::时间服务::". Archived from the original on 2012-06-17. Retrieved 2013-03-16.
  3. ↑ 西安高华科技有限公司 (2020-01-10). "河南商丘BPC电波塔发播时间公布" (in Chinese). Archived from the original on 2021-07-29. Retrieved 2021-07-29.
  4. ↑ Feng, Ping; Wu, Guichen; Bai, Yan; Ding, Xiaofeng (August 2010), Tan, Jiubin; Wen, Xianfang (eds.), "Additional spread spectrum modulation timing method in BPC", Sixth International Symposium on Precision Engineering Measurements and Instrumentation. Proceedings of the SPIE, Proceedings of SPIE, 7544: 75441X–75441X–6, Bibcode:2010SPIE.7544E..1XF, doi:10.1117/12.885845, S2CID 110865336
  5. ↑ Description (in Chinese) Includes sample of time code captured around 2019-12-01 15:52. The time code diagram starts with the seconds field numbered "0" and ends with the marker numbered "19" but note in the text below that it corresponds to second 1, 21 or 41. The screenshot of a waterfall plot with the BPC signal shows that there is no signal reduction at 19:37:40. Unfortunately, the capture only lasts 15 seconds and does not show enough to determine if the encoded time is that of the instant preceding the time code (like WWVB) or following it (like DCF77).
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.