At about 1317 UTC on Sunday, the 17th day of August 2025, I tuned in to XSL ‘Japanese Slot Machine’, transmitting on 4291 kHz.

XSL is a Japanese military station that transmits data in the form of QPSK (quadrature phase-shift keying) at 1500 Bd. It is known as the ‘Japanese Slot Machine’ due to the signal resembling the sounds made by a slot machine. It operates on several frequencies, including 4291 kHz. The XSL signal is transmitted from the Japanese Maritime Self-Defence Force Ichihara Transmitting Station in Ichihara, Japan. (Numbers 2016)

Above: Map showing the location of the Ichihara Transmitting Station. Image c/o mapcarta.com

Below is an aerial view of the Ichihara Transmitting Station.

Above: aerial view of the Ichihara Transmitting Station. Image c/o mapcarta.com

The XSL signal was first reported on the shortwave bands by listeners back in late 2000. (Rogers 2025)

Below is a video of my reception.

References.

1. Number Stations Research – Numbers Stations Research and Information Center. (2016). The Japanese Slot Machine – XSL XSL – Japanese Navy. [online] Available at: https://www.numbers-stations.com/japan/the-japanese-slot-machine/ [Accessed 30 Aug. 2025].‌
2. Rogers, B. (2025). Mystery Signals. [online] Signalshed.com. Available at: http://www.mysterysignals.signalshed.com/page20.html [Accessed 30 Aug. 2025].‌