Over on YouTube user Alex swl has uploaded a video showing his reception of a Very Low Frequency (VLF) radio signal using a laptop running SDRSharp and a Chirio Mini Whip antenna connected directly to the laptop’s sound card input.

Every year on Alexanderson Day (this year on 29/06/2014) and some other days the Varberg VLF Radio Station in Sweden transmits a morse code message using a 1.9 km (1.2 mile) horizontal wire antenna at 17.2 kHz with callsign SAQ. Because the transmission frequency is so low, a standard PC soundcard can be used to directly receive the signal.

Alex swl was able to receive this signal in Italy.