160 meters RFI caused by Nintendo 3DS after market power supply

This past Saturday (November 8, 2014) at approximately 12:30am I encountered RFI on 160 meters that was appearing approximately every 78 khz, and the signal was very broad (approximately 30 khz wide). My 3 fixed pennant RX antennas indicated the signal was at a heading of approximately 123 Degrees, so I grabbed my DX440 portable HF receiver , W1FB preamp, and 14" diameter shielded loop and within 5 minutes I tracked the signal down to a home on an adjacent street that was approximately 150 feet from my house (at a heading of approximately 120 degrees).

Recording of interference on youtube using TS180s with wide CW filter : http://www.youtube.com/watch?v=opSB_E5K1UA&feature=youtu.be

Recording of interference on youtube using DX440 receiver in AM mode with wide filter : http://www.youtube.com/watch?v=4Icy0szkKtI&feature=youtu.be

A spectrum plot of the audio output on an AM receiver (DX-440) showed considerable 120 hertz component (twice that of the 60 hertz line frequency) as shown in the spectrum plot below.

1972 khz

This afternoon (November 11, 2014) my neighbor and I went room to room in his house tracking down the signal using my DX440 receiver and shielded loop antenna (preamp not used, and receiver gain turned down). On the main floor we found the signal strongest right in front of a 120 volt wall receptacle, but could not locate anything nearly as strong on his first floor, and his basement yielded only weaker signals. We then went upstairs (second floor), and tracked the signal down to a Nintendo 3DS that was plugged into a small after market AC/DC converter (wall wart power supply). The signal was only present when the wall wart power supply was plugged in and the 3DS screen was open.

I then ran home and called my neighbor on the phone so we could run some confirmation tests. Sure enough when my neighbor powered the 3DS with the suspect power supply the interference was present at my house, and when he unplugged the power supply the interference disappeared. My neighbor then powered the 3DS with the power supply that came as original equipment with the 3DS, and it appears to work just fine (no RFI heard).

Picture of after market power supply that caused interference on 160 meters when powering a Nintendo 3DS

(click on picture to zoom in)

Website created and maintained by Don Kirk (wd8dsb), 11NO14