SAQ 17·2 kHz Alexanderson Sweden

Alexanderson Day named after the Swedish radio engineer Ernst Fredrik Werner Alexanderson and held either on the last Sunday in June, or on the first Sunday in July, whichever comes closer to 2 July, is the day of the open house at the Swedish government VLF transmitter Grimeton, call sign SAQ, located near Varberg. On Alexanderson Day, Christmas Eve and at other times during the year the only workable Alexanderson alternator transmitter in the world is used to transmit short Morse messages on 17·2 kHz using a 1·9 km (1·2 mile) horizontal wire antenna which should be easily receivable in all of Europe. The transmitter is preserved as a historical remnant of early radio technology and as an example of VLF (Very Low Frequency) equipment.

These transmissions cannot be received by ordinary radios because of their low frequency. Modern enthusiasts often monitor the transmissions using a PC with antenna connected to the soundcard input and appropriate free software (see below) or a short-wave receiver with an upconverter or any of several receivers designed to receive VLF transmissions directly. In recent years, Software-defined radio receivers have proven to be very useful and effective in receiving transmissions from SAQ around the world. Source: Wikipedia

Free SAQrx VLF radio receiver software:

Connect a simple Long Wire antenna (I'm using 20 metres insulated wire 5 metres high) down the garden to the microphone or line-in input to a redundant PC e.g. Windows XP that no longer receives Internet security updates. Best to use a PC not too important as excess static may damage the soundcard. 2 X 1N5406 diodes back to back and as kindly advised by Norman G8ATO of Verulam ARC a 100k Ohm resistor across the PC input as in image below enhances protection. Also, his recommendation of the 4·7nF capactor which serves as a filter. Ground using e.g. large crocodile clip via central heating copper water pipe. All components available from eBay but often sold in bulk so club together to keep cost down e.g. 1N5406 diodes £2 for ten.

At time of writing this (January 2016) I must wait until next SAQ broadcast to know if my effort will work.

It did work! Sunday 03rd July 2016 08:45 UTC to 09:10 UTC approximately. Tune up and message received. Report: 439 QRM & QRN. For most purposes UTC = GMT.

VLF protection and filter

Before turning on ensure all levels are LOW (you may need to attenuate the antenna signal) and be especially careful of overload if wearing headphones.

Instructions for using the software are available from the download page:

Laptop is even better because you can transport it to an EMC quiet zone whilst away e.g. on holiday. Use the SAQrx VLF Radio to listen to the broadcast below:


Alexanderson Day
Grimeton, Varberg, Sweden

Grimeton (call sign SK6SAQ) still transmits a message to the world twice a year: Alexanderson Day (Sunday end of June / beginning of July) & Christmas Eve. Times may vary. Google: "SK6SAQ" to check for updates and sign up for their E-mail newsletters.

Also, SK6SAQ may make test transmissions about 14:00 UTC the day before published broadcast.

Grimeton (call sign SK6SAQ) scheduled to transmit a message to the world on Saturday Christmas Eve 24th December 2016:

Transmit frequency 17·2 kHz

07:30 UTC Alternator started to tune up
08:00 UTC Transmission

Amateur Radio activity may usually be:
7·035 MHz CW
14·035 MHz CW
3·755 SSB
145·700/145·100 FM

QSL via SM bureau

Check details:

p.s. Please be mindful that if using a conventional stand alone radio receiver (possibly with a converter) that switch mode power supplies may generate 'noise' at these very low frequencies. Consider linear power supply or battery.

University of Twente receiver:
Twente is a receiver in Twente in the Netherlands of long wave, medium wave and short wave signals, continuously relaying these signals to the internet. To listen to SK6SAQ, do like this:

Frequency enter 17.2 kHz
Waterfall view 'max in'
Bandwidth 'CW narrow'
Check frequency 17.2 kHz

Good luck!

73 Bob G4PVB


p.s. Text from SAQ TX 24th December 2016