Mode Time signals

Time signals: the time stations and your computer clock against them.

Group	Weather & science
Default frequency	0.0775 MHz
Default sample rate	256 ksps
In the mode list	LF and HF time codes

Step-by-step: Tutorial-Time-signals

What Time signals is

Time stations (DCF77, MSF, WWVB, JJY, WWV and others) broadcast the exact time, so radio clocks can set themselves.

Frequencies and settings

DCF77 (77.5 kHz), MSF, WWVB (60 kHz), JJY (40 / 60 kHz) carrier keying; WWV / WWVH 100 Hz BCD subcarrier and ticks; CHU 300 bit/s FSK (A frames); BPM (China, Pucheng; 2.5 / 5 / 10 / 15 MHz, shares them with WWV so the station is chosen by hand): 1 kHz ticks and pulse-width coded seconds, UTC and UT1 minutes (frame layout assumed, see time_proto.h, not yet checked against a real BPM recording), and BPM coded (the 1 kHz burst code of the pure carrier slots, 2.5 / 5 MHz: every second frame names the date and time, DUT1 to 0.1 ms and the leap count; read from a real recording); BPC (China, 68.5 kHz, 20 s frames of 0.1 - 0.4 s carrier dips, UTC+8, needs an LF radio or upconverter) and HLA (Korea, 5 MHz, 100 Hz pulses, UTC+9). A recording of the demodulated audio and a slow recorder clock can be entered on the Receiver panel. LF needs a radio specified for it (SDRplay, Airspy HF+, RTL-SDR direct sampling); OnAir tries any frequency on any radio and notes when it is outside what the radio is specified for.

Setting	Value
Start frequency	0.0775 MHz
Tuning range of the mode table	0.03 to 30 MHz
Sample rate asked	256 ksps
Lowest working rate	48 ksps
Channel width	10 kHz

OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is LF and HF time codes.

What OnAir shows

Time, date, time zone, summer time and leap second flags, DUT1, the seconds tick and its jitter, the computer clock offset after the path delay from your position, level and SNR history; Clock tab: Sync computer clock (source GPS or time station, shows the measured offset, a Sync now button that sets the clock only after your click through the system's administrator prompt and refuses when the signal is not locked or the offset is over 10 minutes; a command to copy) and an optional Act as NTP server (LAN) switch (off by default, UDP 123 or 1123, stratum 1 "GPS" or stratum 2 from a time station, LAN clients only, rate limited, hobby accuracy).

The mode's own tab has these screens: Time, Minutes, Clock. The other tabs (Overview, Receiver, Scan, History) are described on the Main window page.

Tips and caveats

• The coded BPM signal was read from a real recording; checked with generated signals and impairments; recordings of real signals welcome for the other stations.
• Which radio: Only in direct-sampling mode, which OnAir offers in the radio settings, and the signal may be weak or absent. SDRplay and Airspy HF+ radios reach low frequencies directly.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: Receiving these signals is legal in most countries. OnAir is a receiver. See Legal.

Related pages

• Time stations and the clock
• All modes, Weather & science
• Supported radios, Troubleshooting, FAQ
• More in Weather & science: HRPT / AHRPT, NOAA Weather Radio SAME, Radiosonde, Ionospheric sounders, Radio astronomy