The Alarm: a siren-like marker on 4770 kHz from Smolensk

What you hear

A tone that listeners compare to a siren, repeated without end on 4770 kHz. The resemblance earned the station its name. There is no announcement and no identification, and the sound does not change with the time of day. Compared with the Buzzer, which breaks off for a voice message every so often, the Alarm is a far quieter channel: the catalogue notes that hardly any real traffic has been heard on it since it started in 2019. That makes it an easy station to confirm and a hard one to catch doing anything.

Who transmits and why

The transmitter is near Smolensk, in the west of Russia. By its location, its date and the family resemblance of its signal, the station is thought to be the channel marker of a net of the Western Military District, in the way the Rostov markers are attributed to the Southern one. Nobody has confirmed this, and the attribution should be read as the informed opinion of listeners, not as fact.

What the Alarm demonstrates, better than any of its relatives, is what such a station is for. A marker is not there to carry messages. It holds a frequency in reserve, proves day after day that the transmitter and the path work, and lets everyone on the net recognise the channel by ear in a second. The fact that almost nothing is ever sent over it is not a sign that the channel is useless; it is the normal state of a channel that is kept for the moment it is needed. In that sense the Alarm is the plainest answer to the old question of what the Buzzer is for.

The signal is sent openly in the clear; a listener receives it and nothing more.

When and where to listen

4770 kHz lies in the 60 metre range, between the 80 and 40 metre amateur bands. In daylight the signal is heard a few hundred kilometres from Smolensk; after dark it carries across Europe. The best receivers are in the Baltic states, Finland, Poland and Sweden, where the marker is a daytime signal as well; from Germany, the Netherlands and Britain it is an evening and night signal, weaker but usually there. The frequency lies inside a tropical broadcasting range, so on a winter evening a faint distant broadcaster can sit nearby; the siren's shape on the waterfall sets it apart at once.

The program sets USB; the marker is AM-compatible and AM works as well if the tone sounds odd. As with every marker in this family, whether a voice message ever comes is a matter of luck, and on this station the odds are long.

In ShackDeck

Station catalogue → Mystery stations → The Alarm. The program finds a public receiver that covers 4770 kHz, tunes it and sets USB; no receiver, antenna or account of your own is needed. The siren's pattern is visible on the waterfall before you turn up the sound, which makes it a quick check whether the station is on.