minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky) (01/19/91)
Depends on what precision-stability you want. I once built an FM
transmitter to fly on a bat, for Prof. Griffin's research. It weighed
300 milligrams:
/----------------------------------\
\--Cu-paper-Zn-R-tunnel diode-|--L-/
|-C-/
The paper is acidified. Resistor R is not very critical. The
inductor L was a 1/4" coil of three turns of wire. The capacitor iof
the parallel LC circuit was a capacitance microphone made by
stretching a bit of aluminized mylar over a disk of metal screening
that was slightly dented in the middle.
The bat didn't like it much but managed to fly around anyway.