Have they found many signals in space with those frequencies? I always thought those frequencies would be few and weak. It appears that space is so large, that for EM communication, one is going to need a lot of power. Nature does this by using multiple emitters and emitting a flux. The flux can superposition and acquire the intensity and power needed.
But for lower frequencies, much larger collective structures for the proper wavelength are needed. How large of a structure do you think a plasma will allow.....and for how long?
To call it a radio signal the F must be constant and have repeatable duration. Otherwise, it's just static.
Static is all the superposition of EM, at point of detection. Or at any point in space.
All radio emissions should be much weaker then any light source. Organized structure with the dimension needed would be rare, in my opinion.
But if I had a low frequency receiver array on the far side of moon, I might be pleasantly surprised.