http://www.dself.dsl.pipex.com/MUSEUM/COMMS/ear/ear.htm
There was a brief period between the invention of
aviation and the invention of radar when it was
a military necessity to LISTEN for enemy
aircraft.
Of course, if you paint a modern American warcraft
with a radar signal, you will infallibly be destroyed
with a missile. So I wonder how much surreptitious
listening is going on in Afghanistan and Iraq.
