I recorded this transmission on 7.009 MHz from about 0430 UTC to at least 0515 UTC with no breaks in the transmission on February 27, 1999. The signal strength was a very strong 20dB over S9 here and was also heard all over the U.S. well into the next day. I have performed a spectrum analysis on the signal and I find it very interesting. I have heard this type of transmission many times outside of the amateur bands although they were often in parts of the HF spectrum allocated to shortwave broadcasting or other places where they probably should not of been. It may be the signal that utility monitors often refer to has the "piccolo" that has been used by embassies for decades.
In recent years (after this was recorded) amateurs have began to you a digital mode of communication that is very similar to this one called MFSK-16. This transmission was recorded before the amateurs started using it and since it was one continuous transmission with no breaks for a great number of hours and it had an incredible signal strength it is highly unlikely to have been an amateur transmission.
Here is a breakdown of the signal:
