52-year-old Johan Klinthammar says he was sitting in his car near Björkvik in Sörmland on Thursday when he heard the message, which he did not understand.
He took out his mobile phone and filmed the car radio, whose display showed the text “Alarm message”.
"I reacted strongly. At first I thought the car had gone haywire," says Johan Klinthammar.
The message lasted a few seconds and then the news broadcast continued.
Natural phenomenon
In the video clip, which TT has seen, a male voice warns in Russian of an impending drone attack.
“Stay home, avoid windows or go to a shelter,” the voice says.
According to state-owned Teracom, the most likely explanation is “tropospheric overextension,” a natural phenomenon that occurs when the heat of midsummer gives way to cooler weather. The phenomenon allows radio signals to travel further than they normally would.
Different air layers form at different temperatures and this means that the radio signals can bounce off these layers, says Jan Ossfeldt, network strategist at Teracom.
In this case, according to Ossfeldt, a Russian radio signal from, for example, Kaliningrad or St. Petersburg has probably bounced over the Baltic Sea and been picked up by Swedish radio receivers.
Recently, Ukraine has escalated its retaliatory attacks against targets in Russia, including Saint Petersburg.
Difficult to protect oneself
Ossfeldt says that every year Teracom receives a handful of calls from people in Sweden who have heard messages in other languages on their radios.
It can be perceived as a bit scary if you don't understand what it is, especially considering the situation around the world.
According to him, it is difficult to protect oneself against this type of natural phenomenon.
What you can protect yourself against is ensuring that the information we send out is correct, and there we naturally have strong protection against intrusion if someone tries to intrude, says Jan Ossfeldt.
