The Grimeton Radio Station, located near Varberg on Sweden’s southwest coast, is a remarkable testament to early 20th-century communication technology. Equipped with the last operational Alexanderson alternator—a pioneering high-frequency generator—the station offers a unique glimpse into the evolution of global wireless communication.
Historical Significance
In the early 1900s, as nations sought reliable transoceanic communication methods, Sweden recognized the strategic necessity of establishing its own long-distance radio facility. This led to the construction of the Grimeton Radio Station, which commenced operations in 1924. The station played a crucial role in transmitting telegrams across the Atlantic, particularly during periods when submarine cables were compromised, such as during World War I. Its ability to maintain communication links made it an invaluable asset during global conflicts.
Technical Overview
At the heart of the station is the Alexanderson alternator, an electromechanical device designed by Swedish-American engineer Ernst Alexanderson. This 200 kW generator produces alternating current at radio frequencies, enabling longwave transmissions. The alternator drives a massive rotating element to generate continuous radio waves, which are then transmitted via a 1.9 km long multiple-wire antenna supported by six 127-meter-high steel towers. This setup allows for effective very low frequency (VLF) transmissions, capable of reaching across continents and oceans.
Operational Procedures
Starting the Alexanderson alternator is a meticulous process. Operators initiate the system by gradually bringing the alternator up to its operational speed, ensuring synchronization with the desired transmission frequency of 17.2 kHz. Once stabilized, the transmitter is keyed to send messages in Morse code. This procedure requires precise coordination and expertise, reflecting the engineering marvel of early 20th-century technology.
TX schedule and reception
SAQ, the call sign of the Grimeton Radio Station, typically conducts transmissions twice annually: on Alexanderson Day (either the last Sunday in June or the first Sunday in July) and on Christmas Eve morning. These events commence with the startup of the alternator approximately 30 minutes before the scheduled transmission time. The station may also perform additional transmissions to commemorate special occasions. Detailed information about upcoming transmissions is published in advance on the Alexander Association’s website.
Receiving SAQ’s VLF transmissions at 17.2 kHz requires specialized equipment, as standard radios do not cover such low frequencies. Enthusiasts often use software-defined radios (SDRs) connected to appropriate antennas, such as large loops or long wires, to capture the signal. The received Morse code can then be decoded manually or with software. Detailed reception reports are highly valued by the Alexander Association and contribute to the preservation of this historical practice.
UNESCO World Heritage status
In recognition of its historical and technological significance, the Grimeton Radio Station was inscribed on the UNESCO World Heritage List in 2004. It stands as the only remaining example of a transatlantic VLF station equipped with an Alexanderson alternator that is still operational. This designation underscores the station’s importance as a cultural and scientific landmark, preserving the legacy of early global communication efforts.
Interesting Facts
- Global Reach: Despite its age, SAQ’s transmissions can be received across Europe and have been reported as far away as North America and Australia, demonstrating the enduring efficacy of VLF communication.
- Community Engagement: The Alexander Association, a dedicated group of volunteers, maintains the station and organizes events, ensuring that this piece of living history remains accessible to the public.
- Educational Value: The station serves as an educational resource, offering insights into the evolution of communication technology and the engineering feats of the early 20th century.
The Grimeton Radio Station not only preserves the legacy of early wireless communication but also continues to engage and inspire individuals worldwide through its annual transmissions and educational initiatives.