MSF: the British time signal from Anthorn on 60 kHz

What you hear

In CW mode MSF is a note that keeps getting interrupted. At the start of every second the transmitter switches its carrier off completely, for a tenth of a second at least, so the note has a clean gap in it sixty times a minute. The gap is often longer: the bits of the time code are sent as extra tenths of silence, one window for the A bit and one for the B bit, so some seconds start with a short gap, others with one two or three times as long. At the start of the minute the carrier stays off for half a second, a pause you cannot miss. That is the whole trick, on-off keying rather than the dips of DCF77, and it makes MSF the easiest of the European time signals to follow by ear.

The code within the minute carries the year, month, day, weekday, hour and minute in binary-coded decimal, a figure for DUT1 in the first sixteen seconds, and flags that say whether British Summer Time is in force or about to change. Parity bits near the end let a clock reject a corrupted minute.

Who transmits and why

The time comes from the National Physical Laboratory at Teddington, which keeps the United Kingdom's time scale, and the transmitter stands at Anthorn on the Cumbrian shore of the Solway Firth, on a site that also carries a very-low-frequency naval transmitter. MSF began at Rugby in 1950 and moved to Anthorn in 2007 when the Rugby site was closed; a contractor runs the equipment for NPL. The signal is sized to cover the British Isles, with about 17 kW radiated, and it does that with margin to spare: the clocks on British railway platforms, radio-controlled watches, central heating timers and a good deal of industrial equipment all take their time from it.

60 kHz is a busy frequency worldwide. WWVB in Colorado and JJY in Japan use it too, each covering its own continent, and they never meet.

When and where to listen

Any time of day, from a receiver that covers long wave. From the British Isles, the Netherlands, Belgium, northern France and Denmark the signal is strong and steady; from Germany, Scandinavia and Poland it is still comfortable, and at night, when the sky wave adds to the ground wave, it reaches farther still, with slow fades as the two waves drift in and out of step. Because the keying is complete, the note disappears entirely in the gaps, and on a waterfall the carrier looks like a dashed line rather than a solid one.

NPL announces maintenance breaks in advance, usually a few hours on a weekday and occasionally a whole day, so an empty frequency is not necessarily a sign of trouble at the receiver. DCF77 on 77.5 kHz and RBU on 66.66 kHz are a few turns of the dial away, and comparing the three is a pleasant way to learn how each country chose to encode the same thing.

In ShackDeck

Station catalogue → Time signals → MSF (60 kHz). The program picks a public receiver that covers 60 kHz, tunes it in CW with a narrow passband so that the carrier comes out as a note, and shows the waterfall with its dashed line. No receiver, antenna or account of your own is needed.