[airbreather]

I used to build crystal sets that would have two receivers in - one to harvest power from the strongest local station and then a second one that would take some of that power to bias up the detector diaode or to even use a germanium transistor to amplify the audio.

The first receiver would be able to drive a loudspeaker through a transformer loud enough you could hear it across a quiet room, so some power there, but only milliwatts.

I have wondered if these days with the zero volt FETS if there would be enough power for a regenerative receiver, some kind of negative resistance version seems most likely.