Not sure which subject this should be in but here goes.
When I was a kid I experimented sending audio through 3 ground probes, the audio came from a car radio with reasonable o/p power, through an mains trans connected in reverse to step up the volatge into the probes arranged in a triangle, the 'point' being signal and the rear 2 being 'ground'
I got around 50m range or so with plenty of mains hum.
I wondered recently whether I could improve this range to a few hundred meters, mainly for 2 applications wireless comms to an underground bund stores and another for a means of communication that is unlikely to be detected (only because it wouldnt be thought about by eaves droppers).
Reading about ground dipoles it appears that they are capacitive rather than inductive, and a lot of the signal is shorted by the low dc resistance of said ground.
I know subs use 76hz as a means of comms.
When I was a kid I experimented sending audio through 3 ground probes, the audio came from a car radio with reasonable o/p power, through an mains trans connected in reverse to step up the volatge into the probes arranged in a triangle, the 'point' being signal and the rear 2 being 'ground'
I got around 50m range or so with plenty of mains hum.
I wondered recently whether I could improve this range to a few hundred meters, mainly for 2 applications wireless comms to an underground bund stores and another for a means of communication that is unlikely to be detected (only because it wouldnt be thought about by eaves droppers).
Reading about ground dipoles it appears that they are capacitive rather than inductive, and a lot of the signal is shorted by the low dc resistance of said ground.
I know subs use 76hz as a means of comms.