BPC (time signal)
Time signal radio station in China From Wikipedia, the free encyclopedia
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 34.457°N 115.837°E.[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 (21:00–01:00 UTC).[3] BPC includes both a conventional amplitude-modulated time code transmitted during the first 400 of each second, and an additional phase-modulated spread-spectrum time code transmitted during the last 600 ms of each second, about which little is known.[4]
Time code
Summarize
Perspective
BPC transmits the time every 20 seconds, using an amplitude-modulated binary code sent at 2 bits per second. Each 20-second block encodes the China Standard Time of the beginning of that block.[5]
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:
| Duration | MSbit | LSbit |
|---|---|---|
| 0 ms | Start of time code | |
| 100 ms | 0 | 0 |
| 200 ms | 0 | 1 |
| 300 ms | 1 | 0 |
| 400 ms | 1 | 1 |
If there is no signal reduction at all, that is a special marker which marks the beginning of the time code.
| Second | MSbit LSbit | Meaning | Second | MSbit LSbit | Meaning | |
|---|---|---|---|---|---|---|
| 00 | — | Start of time code No signal gap |
10 | 12 P1 | Hour (0=AM 1=PM) Even parity over 01–09 | |
| 01 | 40 20 | Second (00, 20 or 40) | 11 | 0 | Unused | |
| 16 | Day of month (01–31) | |||||
| 02 | 0 0 | Unused | 12 | 8 4 | ||
| 03 | 8 4 | Hour (00–11) | 13 | 2 1 | ||
| 04 | 2 1 | 14 | 8 4 | Month (01–12) | ||
| 05 | 32 16 | Minute (00–59) | 15 | 2 1 | ||
| 06 | 8 4 | 16 | 32 16 | Year (00–99) | ||
| 07 | 2 1 | 17 | 8 4 | |||
| 08 | 0 | Unused | 18 | 2 1 | ||
| 4 | Day of week 1=Monday 7=Sunday | |||||
| 09 | 2 1 | 19 | 64 | |||
| P2 | Even parity over 11–18 |
Note that the bits sent in the same second as the parity bits are not parity-checked.
References
External links
Wikiwand - on
Seamless Wikipedia browsing. On steroids.