On April 1 2015 at 2330z I was monitoring 13554.91 kHz USB with ARGO QRS
spectrum display. There was no activity.
At 2334z a square wave appeared for about for about 120 seconds, then stopped. See the link below for the waterfall capture. I started the QRS view within a second of the appearance of the signal.
At 2346z "EH" become started, about 10 hz lower exhibiting a slight drift occasionally, and has been steady for over an hour. Maybe EH was in testing mode for a few minutes? I don't think so as the shape of the square wave on this unidentified signal doesn't match the "EH" square wave when viewed on the waterfall display.
This is a screen shot of the short-duration square wave copied on 13554.91 kHz + 590 Hz:
http://1drv.ms/1CyFo4PDag