On Sun, 17 Jun 2007 15:19:59 -0700, Radium
wrote:

What is the minimum amount of photons-per-second needed for a 150 KHz
AM radio carrier wave to transmit audio signals? Around 20,000-photons-
per-second?

That one is real simple:
2 photons (of appropriate amplitude, hence color) at most 3.333 (less
would be better, but not too much less) microseconds apart.

Feel free to desire more, but you asked for the minimum. If you want
more audio (sideband) content, that will certainly drive up the count
too.

Now, how's your quantum efficiency these days? (Use it to boost the
count higher.)

73's
Richard Clark, KB7QHC