While looking a some VJ clips as a bit of inspiration for an upcomming gig, I came accross this video(0:05 is the important bit)-
Is it possible to broadcast in all frequencies?
I know when I go through the Dartford tunnel they have a system that enables the tunnel operators to communicat via the cars FM radio, so perhaps the same princelple.
But to cover a big range seems quite a chanllenge. It could probably be done sequentially, but in one go?
Maybe a morse signal would work.
Anyway, just an off topic thought.