I see 15 Kilowatt audio amplifiers advertised,
therefore there must be a speaker system, public address horns available for
such amplifiers.
If one of these speaker horns was directed line
of sight towards the horizon or a mountain top and a suitable dish
positioned at the receive end, it must be possibel to intercept such a
signal at audio frequencies. eg Transmit a tone which could be keyed at
9 - 20 Kcs and see what distance could be covered.
Keeping the signal just above the
normal human audio range would avoid interference.
or just TX a signal at say 5 Kcs and see
how far it could be heard by ear with this sort of power, maybe further
than the same signal transmitted by radio means, except one had an
exceptionally large antenna
Maybe a NOV is required for this
experiment!!!!
de g3kev