Northwood weather fax: Royal Navy weather charts on 8040 kHz

What you hear

The same kind of sound as any marine fax: a rasping tone with a half-second rhythm, a start tone before each chart and a stop tone after it, about ten minutes per picture at 120 lines a minute. Decoded, the charts carry the marks of a naval weather office: surface analyses and prognoses for the North Atlantic and Europe, charts for the Mediterranean, upper-air charts at 500 hPa, sea state and swell, and now and then the broadcast's own timetable, sent as a chart so that a ship can see what is coming. The frame carries the callsign GYA, the Royal Navy's station at Northwood.

Who transmits and why

Northwood, in the north-west of London, is the headquarters of the Royal Navy's fleet and of its weather service, and the fax broadcast carries its name; the transmitters themselves stand elsewhere in Britain. The charts are drawn for the fleet, but the broadcast is in the clear, and merchant ships and yachts in the eastern Atlantic have used it for decades as a second source beside the civil services. Four frequencies carry it: 2618.5 kHz at night for ships close in, 4610 kHz for the night, 8040 kHz for day and night and 11086.5 kHz for the daytime. As with every fax station, the dial in upper sideband is set 1.9 kHz below the nominal frequency, which is why the catalogue shows 8038.1 kHz.

One honest warning: naval broadcasts change more often than civil ones. The chart set, the timetable and even the frequencies have been revised over the years, and listeners have reported quiet periods. If 8040 kHz is silent for an hour, try 4610 or 11086.5 kHz before deciding that the station is off the air.

When and where to listen

8040 kHz is the main frequency for Europe. From Britain and Ireland it is loud at any hour; from the Netherlands, Germany, France and Scandinavia it is clean most of the day and all night, and from Spain or the Baltic states it is usable with some fading. Charts come in groups a few times a day with gaps between them, so a quiet frequency usually means a gap, not a fault. A receiver within a thousand kilometres of Britain gives the best picture.

In ShackDeck

Station catalogue → Aviation → Northwood weather fax (8040 kHz). The program finds a public receiver with the frequency, tunes it to 8038.1 kHz and sets the WEFAX mode; the chart builds up on screen line by line from the start tone onwards. No receiver, antenna or account of your own is needed. For the DWD charts from Germany, which use the same format, see the Pinneberg article.