I've been a radio enthusiast since the early 1980s, but it wasn't until recently that I finally got myself a receiver and antenna suitable for listening to VLF (3-30 kHz) (see my earlier blog posting here).
One of my goals with the new VLF setup was to receive one of the special CW transmissions on 17.2 kHz from historical radio station SAQ Grimeton in Sweden.
Grimeton Radio was built during the years 1922-1924 to provide a "longwave" wireless telegraphy transmitting and receiving station for transatlantic telegram traffic with the United States. The first transmitter used was a VLF machine transmitter invented and designed by Swedish engineer Ernst Alexanderson. Grimeton Radio went on the air in December 1924 with the callsign SAQ. Initially transmissions were done on the frequency of 16.1 kHz but this was soon changed to 17.2 kHz.
|The Alexanderson alternator transmitter at Grimeton Radio (source)|
After some years, new technology had made the Alexanderson machine transmitter obsolete for its original purpose; by the 1930s transatlantic communication had gradually started to switch to shortwave, and vacuum tube shortwave transmitters were used instead. The Alexanderson transmitter was still used however to communicate on VLF with submerged submarines, and wasn't decommissioned until the 1990s. Luckily the complete site of Grimeton Radio, including the original VLF machine transmitter, has been preserved as a historical monument. In 2004 the radio station was added to UNESCO's List of World Heritage Sites.
Like mentioned earlier, the original VLF machine transmitter at Grimeton Radio was designed by Swedish engineer Ernst Alexanderson. It consisted of an alternating-current generator (the so called Alexanderson alternator) driven by an electrical motor through a speed-increasing gearbox. When driven at high speed at the correct RPM, the alternator generates a signal on 17.2 kHz. Yes, this means that RF is generated without any electronic parts (like tubes or transistors) involved at all!
Although not in regular use anymore, two or three times a year on special days a CW message is transmitted by Grimeton Radio using this very same historical Alexanderson alternator transmitter!
Traditionally, one of the special transmissions is done in the morning of Christmas Eve, and so was the case this year. And I was extremely happy to manage to catch it! For the first time I was listening to this special station, to a Morse Code transmission generated by a historical, pre-electronic transmitter, the only one of its kind remaining! And on one of the most beautiful and magical days of the year! Goose bumps!
|Grimeton Radion at - 6ºC on the morning of Christmas Eve 2018 (source)|
The signals were picked up at PA7MDJ with an SDRPlay RSP1A receiver and a MegActiv MA305FT E-field probe antenna. Below on my SoundCloud account you can listen to the recording I made this beautiful Christmas Eve morning, December 24th, 2018.
The transcript of the received Morse Code message reads as follows:
CQ CQ CQ DE SAQ SAQ SAQ =
THIS IS GRIMETON RADIO / SAQ
IN A TRANSMISSION USING THE ALEXANDERSON 200 KW ALTERNATOR
ON 17.2 KHZ =
WE WISH YOU ALL A MERRY CHRISTMAS AND A HAPPY NEW YEAR =
SIGNED: THE WORLD HERITAGE AT GRIMETON
AND THE ALEXANDER-GRIMETON VETERANRADIOS VAENNER ASSOCIATION AR =
FOR QSL INFO PLEASE READ OUR WEBSITE:
WWW.ALEXANDER.N.SE II WWW.ALEXANDER.N.SE =
DE SAQ SAQ SAQ SK
The message was preceded by a "VVV VVV VVV DE SAQ SAQ SAQ" loop.
In 2003 I visited the Grimeton Radio site to look for a geocache (one of my other hobbies), unfortunately without the possibility to take a look inside the transmitter building, but that's another story.
https://www.youtube.com/watch?time_continue=2719&v=shqi43EV07c - Video made at Grimeton Radio during the special Christmas Eve 2018 transmission