Transmission Format
BPM transmits different signals on a half-hour schedule, modulated with 1 kHz audio tones to provide second and minute ticks:
| Minute | Duration | Transmission | |
|---|---|---|---|
| 00 | 30 | 10 | UTC: 10 ms second ticks, 300 ms minute ticks. |
| 10 | 40 | 5 | Carrier (no time code) |
| 15 | 45 | 10 | UTC: 10 ms second ticks, 300 ms minute ticks. |
| 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 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.
BPC includes both a conventional amplitude modulated time code and an additional spread-spectrum time code, about which little is known.
Read more about this topic: BPM (time Service)