At low frequencies amateur signals are very weak.
Amateurs use ordinary morse code to communicate at
very poor S/N ratios.
The morse code bit may be up to 120 seconds and the
keying is decoded visually on a waterfall diagram.
To get some input for the development of a qrss mode in Linrad I have made a test recording on 137 kHz with some amateur qrss signals present in it. The date was June 17 2003, approximately 22.25 to 23.00 UTC. The antenna was a single turn rectangular coil with side lengths 2 x 4 meters. The long wires were horizontal and the coil center 5 meters above ground. The coil was oriented with its zero direction SE - NW.
The file is about 1.2 gigabytes and contains several different types of interference on top of the amateur generated signals.