A few people are currently experimenting with sound powered RF transmitters, generating the DC power to run a microwatt level oscillator from the human voice or morse key activation. There have been a few such ideas published. What appeals to me is a sound powered TX coupled with a crystal set RX. Such a system might get a mile or two as long as the station at the far end was running a few watts of AM or MCW. This would be the ultimate in QRPp!There is a patent for this sort of sound powered transmitter - see United States Patent US2981833 dating from 1955 which has some schematics. This is available to view at http://www.freepatentsonline.
