Ari Silversteinn wrote:
Are you saying that if I am attempting an overbroadcast on, say, 680 AM and
the station is doing the same, and I am 12 db + greater, that all we will
get is squeal?

One signal is the Beat Frequency Oscillator. I am amazed
that no one has thought of this perfect solution before.

If Morse code were required for all driver's licenses, then
all you have to do is furnish a CW carrier wave. The two
signals would mix and the squeal would be Morse code which
would carry the emergency information.
--
73, Cecil, http://www.qsl.net/w5dxp