Alexanderson Day is the day of the open house at the Swedish government's

VLF transmitter Grimeton Grimeton Radio Station () in southern Sweden, close to Varberg in Halland, is an early longwave transatlantic wireless telegraphy station built in 1922–1924, that has been preserved as a historical site. From the 1920s through the 1940s it wa ...

, call sign SAQ, located near

Varberg Varberg () is a Urban areas in Sweden, locality and the seat of Varberg Municipality, Halland County, Sweden, with 35,782 inhabitants in 2019. Varberg and all of Halland are well known for their "typical west coast" sandy beaches. In Varberg th ...

. Named after the Swedish radio engineer Ernst Fredrik Werner Alexanderson, it is held either on the last Sunday in June, or on the first Sunday in July, whichever comes closer to 2 July. On Alexanderson Day, Christmas Eve, and at other times during the year, the only workable

Alexanderson alternator An Alexanderson alternator is a rotating machine, developed by Ernst Alexanderson beginning in 1904, for the generation of high-frequency alternating current for use as a radio transmitter. It was one of the first devices capable of generating th ...

transmitter in the world is used to transmit short

Morse Morse may refer to: People * Morse (surname) * Morse Goodman (1917-1993), Anglican Bishop of Calgary, Canada * Morse Robb (1902–1992), Canadian inventor and entrepreneur Geography Antarctica * Cape Morse, Wilkes Land * Mount Morse, Churchi ...

messages on 17.2 kHz, which should be easily receivable in all of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. The transmitter is preserved as a historical remnant of early radio technology and as an example of

VLF Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave ...

(Very Low Frequency) equipment. These transmissions cannot be received by ordinary radios because of their low

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

. Modern enthusiasts often monitor the transmissions using a PC with a coil connected to the

soundcard A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio i ...

input and

FFT A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). A Fourier transform converts a signal from its original domain (often time or space) to a representation in ...

analysis software, or a short-wave receiver with an upconverter, or any of several receivers designed to receive

transmissions directly. In recent years,

Software-defined radio Software-defined radio (SDR) is a radio communication system where components that conventionally have been implemented in analog hardware (e.g. mixers, filters, amplifiers, modulators/ demodulators, detectors, etc.) are instead implemented ...

receivers have proven to be very useful and effective in receiving transmissions from SAQ around the world.

References

{{reflist

External links

Alexander Friendship Association Home PageAlexanderson Day Youtube
video of equipment in operation History of radio technology June observances July observances Year of establishment missing