Listening to BBC radio using a storm detector circuit , 1346 km away from London

Just another appliance for a simple storm detector (10kHz antenna + amplifier). In the night time I'm able to listen to some radio stations several hundreds of km away, probably due to better propagation conditions. I'm not sure how it works anyway.

Schematic: https://www.electroschematics.com/storm-detector-circuit
connected to a pc speaker amplifier

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