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.
3 comments:
I may be wrong but some sort of "sound powered" transmission was used in the US Navy during WW2 on ships. At least I think so.
Sound-powered handsets are usually repaired on location because they are permanently connected. When trouble develops in a sound-powered headset-chestset, the usual procedure is for the operator to bring it to the
IC shop and exchange it for a good one.
I have just got a copy of Mike Rainey's Code Talker voice powered transmitter working. Boy does it take some 'voice' to get the thing to generate enough AC at enough power to rectify to enough clean DC to make the oscillator start without chirping. But it works! Great fun. Now the experimenting REALLY starts.
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