Transmissions by U.S. amateurs involved in experimental very low frequency (VLF) operation have been monitored by amateurs in Europe. The ARRL Letter reports that transmissions by hams operating under the WH2XBA experimental license on frequencies of approximately 74 kHz and 29.5 kHz were received in both the UK and in Germany. The transmissions use very slow speed Morse code, with each "dit" lasting two minutes and each "dah" lasting six minutes (not exactly a mode for quickly transmitting large amounts of information - ed.).
The Letter also reports that the software being used to detect these signals is also being used by U.S. Navy personnel assisting in the search for missing Malaysian Flight 370 to listen for "black box" pings transmitted at 37.5 kHz.