DWD weather fax on 7880 kHz: charts from Pinneberg, day and night

What you hear

In plain USB the station is a steady tone that flickers and rasps: a chart is going out at two lines a second, and every line is a sweep of audio between 1500 Hz for black and 2300 Hz for white. Between charts the transmitter holds a clean tone at the white level, so a quiet carrier does not mean the station is off. Each chart opens with a start tone of 300 Hz for a few seconds, then phasing pulses, a thin white stripe repeating on the waterfall, then ten to twenty minutes of lines, then a stop tone of 450 Hz. The format is the marine standard, 120 lines per minute with IOC 576, what a ship's fax receiver prints on paper.

Decoded, the pictures are the working charts of the marine weather office in Hamburg: surface analyses with isobars and fronts for the North Atlantic and Europe, pressure forecasts from 12 to 108 hours ahead, 500 hPa and 850 hPa charts, wave forecasts for the North Sea and the Atlantic, sea-surface temperature, and in winter ice charts for the Baltic. DWD also transmits its own schedule as a chart in the early afternoon UTC, the reliable way to learn this season's programme.

Who transmits and why

Deutscher Wetterdienst, the German national weather service, has sent fax to ships for decades from its transmitter at Pinneberg, north-west of Hamburg. The charts are drawn by the marine weather office in Hamburg. On 7880 kHz the callsign is DDK3; the same programme runs on 3855 kHz as DDH3 at night and on 13882.5 kHz as DDK6 in the daytime. The audience is ships without a data link, yachts on the North Sea and the Atlantic, and anyone who wants a chart straight from the forecaster, with no website in between.

When and where to listen

7880 kHz is the all-day frequency. By day it covers Germany and the neighbouring countries; after dark it reaches most of Europe. The charts run from the early morning, the first surface analysis at about 04:30 UTC, into the evening, with pauses between them. Fax is unforgiving of noise: every burst becomes a speckle on the chart, so a strong signal matters more than it does for voice. Receivers in northern Germany hear the station almost clean; the Netherlands, Denmark and Poland work well; from southern Europe the chart is readable but grainy, and at that distance 13882.5 kHz in the afternoon is usually better.

One detail trips up hand tuning. The chart is carried as frequency modulation of an audio tone around 1900 Hz, so the receiver must sit in USB 1.9 kHz below the nominal frequency: 7878.1 kHz, not 7880. Tuned to 7880 itself the tones fall outside the decoder's window and nothing comes out.

In ShackDeck

Station catalogue → Fax and digital signals → Fax DWD 7880 kHz (day and night). The program picks a public receiver in Germany that has the frequency, tunes it to 7878.1 kHz in USB, sets the WEFAX mode and starts the fax decoder; no receiver, antenna or account of your own is needed. The waterfall shrinks to a spectrum line and the chart grows under it, line by line, as it arrives. If you arrive in the middle of a chart the decoder locks onto the line rhythm and starts from the current line, shifted sideways by some random amount. DWD sends its charts turned by 90 degrees, so the finished chart appears sideways; that is how it is transmitted, not a fault. On the stop tone the picture is cut to its real height and can be saved as a PNG.