Shanwick Radio: North Atlantic position reports on 5598 kHz

What you hear

Long silences, then a voice with the slight compression of an aircraft radio: "Shanwick, Speedbird two one three, position." A pause, and an operator with an Irish accent answers: "Speedbird two one three, Shanwick, go ahead." The crew reads a line of numbers: the latitude and longitude they have just crossed, the time, the flight level, the estimate for the next point and the name of the one after it. Shanwick reads it all back, the aircraft confirms, and the frequency goes quiet again. Between reports there are SELCAL checks: a crew entering the ocean asks for one, and you hear two short two-tone chimes, the code that makes the aircraft's receiver ring like a telephone so that the crew does not have to listen to static for hours.

The callsigns are the airlines' radiotelephony names: Speedbird for British Airways, Shamrock for Aer Lingus, United, Delta, Lufthansa, Air France, with the occasional military or business aircraft among them.

Who transmits and why

Shanwick is the oceanic control area over the eastern half of the North Atlantic, between European and North American airspace. The name is a blend of Shannon and Prestwick: the controllers who plan and separate the traffic sit at Prestwick in Scotland, and the radio operators who talk to the aircraft on HF are at the Shannon aeronautical station in County Clare, Ireland. Beyond VHF range, which ends a couple of hundred kilometres out to sea, HF was for decades the only link, and a position report every ten degrees of longitude was how the controllers knew where everybody was.

Today most aircraft crossing the ocean send their positions automatically by satellite datalink, so HF voice carries much less than it used to: SELCAL checks on entry, reports from aircraft without datalink, and whatever has to be said when the datalink fails. It is still a working safety channel, and the operators are on it around the clock.

When and where to listen

5598 kHz belongs to one of the families of North Atlantic HF frequencies that Shanwick shares with Gander, Santa Maria and New York, so you may hear the other stations too. It is the frequency of the European night and early morning, when the lower band carries: from receivers in Ireland, Britain and Iceland the ground station is a strong signal, and the aircraft, transmitting from high over the ocean, are heard surprisingly well across the whole of western Europe. The busiest hours are the eastbound stream in the night and early morning UTC and the westbound stream in the afternoon; by day the traffic moves up to 8906 kHz, which has its own row in the catalogue.

Upper sideband is the mode, as for all aeronautical HF. Be ready for long waits: this is a working frequency, not a broadcast, and a quiet ten minutes is normal.

In ShackDeck

Station catalogue → Aviation → Shanwick ATC. The program picks a public receiver that covers 5598 kHz, tunes it and sets USB; you need no receiver, antenna or account of your own. If the frequency stays silent in daylight, the daytime row Shanwick ATC 8906 is the one to try.