BSF (time service)
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BSF is the callsign of the time signal transmitter for Taiwan, which transmits time information on 77.5 kHz in the longwave range, and 5 MHz & 15 MHz in the shortwave range from Chung-Li. The longwave transmitter, which uses a T-antenna is situated at Coordinates: .
Due to "low demand", the short wave of BSF was discontinued as of July 1, 2004. The time signal is currently transmitted at a low frequency of 77.5 kHz
The longwave transmitter of the station uses 1 kW of power, achieving an effective radiated power of 460 W. Each second, two bits of information are transmitted using amplitude-shift keying, making 120 bits per minute.
The format is similar to that of WWVB, reducing the carrier amplitude by 10 dB on the second, and encoding information via the time when it is restored. However, BSF uses five possible times to communicate two data bits per second, or a special synchronization mark:
- 0.2 seconds of reduced power and 0.8 s of full power means 00
- 0.4 seconds of reduced power and 0.6 s of full power means 01
- 0.6 seconds of reduced power and 0.4 s of full power means 11
- 0.8 seconds of reduced power and 0.2 s of full power means 10
- No reduced power and 1.0 s of full power means SYNCH, a synchronization mark
Note that the data is Gray coded so that confusion between 0.4 and 0.6 seconds of full power will only corrupt one data bit, and thus be detectable by the parity bits.
Each minute is divided into two blocks. The first 40 seconds are used to broadcast 76 bits of non-time information (weather, disaster warnings, etc.), and the last 20 seconds are used to broadcast the time, as follows:
|:00||0||Always 00||:40||0||Always 01||:50||2||Day of week|
|P1||Time parity||P2||Date parity|
|4||Day of week|
Although bits are reserved for daylight saving time information, they are currently always broadcast as zero, as Taiwan does not observe DST.
The shortwave transmitter on 5 MHz operates continuously, while that on 15 MHz has an interruption from 35 to 40 minutes after the hour. Except for this, the broadcast repeats every 10 minutes.
Each second is marked with a 5 ms tick of 1000 Hz tone, amplitude modulated. At the start of each minute, the tick is lengthened to 300 ms. DUT1 is transmitted by doubling some ticks: seconds :01 through :08 for DUT1 of +0.1 through +0.8 seconds, and seconds :09 through :16 for DUT1 from −0.1 through −0.8 seconds.
Each tick is preceded and followed by 40 ms of silence. The remaining "background" is filled on a 10-minute schedule:
- For the first 5 minutes (:x0:00 through :x4:59), a background 1000 Hz tone is transmitted.
- For the next 4 minutes (:x5:00 through :x8:59), no background tone is transmitted, only the ticks.
- During minute 9 (:x9:00 through :x9:59), voice call sign and time announcements are made in Taiwanese Mandarin.
This schedule repeats every ten minutes, on the hour, except for the previously mentioned 5-minute interruption on 15 MHz.
- Wu, Sz-Hsien (11 September 2014). "A Time Signal Station Project in Taiwan: Overview". Retrieved 2017-04-21.
- "Standard Time and Frequency Broadcast". - in chinese