Ikkunarajoitus

Ikkunarajoitus is a term used to describe a navigational aid deployed by the Finnish Defence Forces, primarily for domestic use, during World War II. The system involved a network of coastal radio transmitters, located on the west coast of Finland, specifically Lappträsk (now known as Lappajärvi) in Southwestern Lapland, and several other stations in the region.

Ikkunarajoitus, Finnish for "coastal observation", comprised an array of 50-kilowatt transmitters. These were used to transmit short sequences of Morse code, as part of a coordinated radio beacon system, used to help Finnish civilian navigation in the Gulf of Bothnia. This region was particularly important for the shipping industry. The transmissions were also intended to support Finnish fishermen, helping them to plot their positions in the dense fogs and freezes of the region.

Amidst reports of German espionage efforts in Finland, Ikkunarajoitus' radio transmissions potentially served as a simple method to alert ships to the presence of suspicious vessels. Although, its effectiveness in this role remains unclear.

The impact of Ikkunarajoitus on the wider conflict remains relatively minor. Despite gaining increased scrutiny following evidence of friendly German espionage, ongoing analysis highlights the system's primary purpose. This aimed to better enable the safe and efficient movement of Finnish shipping within the hazardous and contentious conditions experienced in the Gulf of Bothnia during WWII.

The operation of Ikkunarajoitus lasted into 1947, it's primary objective gradually becoming increasingly inconsistent with changing wartime conditions.