Long time ago I was involved in recording man-made noise and distant thunderstorms, reflected from ionosphere, around 27kHz (yes, kHz.... just above audio band). (Atmospherics)
While this may sound to be trivial, it is actually indirect observation of the Sun's activity, as this noise level was directly affected by Sun (the received signal was properly filtered, rectified and averaged so it represented a slowly changing DC voltage that was easily recorded on the paper tape by mechanical chart-recorder).
Some details on this are available here: http://www.ann-geophys.net/25/2175/2...-2175-2007.pdf
The effect is most prominent just prior to dawn
This may be much easier than SW band (as an antenna, you need just a long wire between two trees, 10-20 metres apart).
The receiver is actually an audio amplifier (with 27kHz filter at front), rectifier + LP filter and DC voltage recorder...