Frequency Usage
The time code consists of a series of signals on multiple frequencies. Transmission starts on the hour. Each time a new frequency is selected, there is 1 minute of low power while the transmitter is adjusted, then full-power transmissions begin.
The transmitters are estimated to operate at 1000 kW, achieving 30–50 kW EIRP. (The difference is due to the low efficiency of antennas at this frequency, which must be much smaller than the 12 km wavelength.)
| Frequency | Minutes | Signal | |
|---|---|---|---|
| Start | Duration | ||
| 25.0 kHz | :00 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :01 | 5 | Unmodulated carrier | |
| :06 | 1 | Morse code call sign, on-off keying | |
| :07 | 3 | Unmodulated carrier | |
| :10 | 3 | On-off modulated with 40 Hz square wave | |
| :13 | 9 | Time code, on-off modulation | |
| :22 | 3 | On-off modulated with 40 Hz square wave | |
| 25.1 kHz | :25 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :26 | 4 | Unmodulated carrier | |
| 25.5 kHz | :30 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :31 | 4 | Unmodulated carrier | |
| 23.0 kHz | :35 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :36 | 5 | Unmodulated carrier | |
| 20.5 kHz | :41 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :42 | 5 | Unmodulated carrier | |
| Off | :47 | Transmission ends | |
The time code consists of a series of carrier pulses:
- Each 100 ms, a 25 ms burst of carrier is transmitted
- Each second, a 100 ms burst of carrier is transmitted
- Each 10 s, a 1 s burst of carrier is transmitted
- Each minute, a 10 s burst of carrier is transmitted
The hour or date is not coded.
Most of the stations were built in the 1970s. RJH63, built later, has a different transmission:
| Frequency | Minutes | Signal | |
|---|---|---|---|
| Start | Duration | ||
| 25.0 kHz | :00 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :01 | 5 | Unmodulated carrier | |
| :06 | 1 | Morse code call sign, on-off keying | |
| :07 | 2 | Unmodulated carrier | |
| :09 | 2 | On-off modulated with 40 Hz square wave | |
| :11 | 9 | Time code, on-off modulation | |
| 25.1 kHz | :20 | 2 | Transmitter tune-up, low-power unmodulated carrier |
| :22 | 1 | Unmodulated carrier | |
| 25.5 kHz | :23 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :24 | 2 | Unmodulated carrier | |
| 23.0 kHz | :26 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :27 | 4 | Unmodulated carrier | |
| 20.5 kHz | :31 | 1 | Transmitter tune-up, low-power unmodulated carrier |
| :32 | 4 | Unmodulated carrier | |
| :36 | 4 | Digital data, ±50 Hz frequency-shift keying, 50 baud | |
| Off | :47 | Transmission ends | |
Read more about this topic: Beta (time Signal)
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