[sdiy] generators/antennas analogy?

[Lincoln Fong]

Whilst I am familiar with the idea of 'back emf' in a generator there is
something I have never understood which Im sure someone can clear up.

I once heard that Radio and TV stations can judge audience figures by the
amount of power 'absorbed' ie the Watts or MWatts they have to pump out. On
one level this makes sense. A popular station would need only the weakest of
transmitters if this were not so. But can the resonance of millions of tuned
circuits really indicate power usage that accurately? And if not then how do
they judge audience figures? I don't really buy the argument that grid power
usage can accurately reflect these things when so many programmes start at
exactly the same time.

Lincoln