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| Joined: | Sep 22nd, 2008 |
| Location: | Doylestown, Pennsylvania USA |
| Posts: | 130 |
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The Raudive detector circuit is a simple radio receiver that responds to a broad band of radio frequencies and rectifies the amplitude variations. The coil is an inductor wound on an insulated form that blocks radio signals but is easily conductive of direct currents and low audio frequencies. The value of the coil is selected to tune radio frequencies present in atmospheric noise. More than one frequency appears at the antenna at one time. An AM radio that is tuned to an unused frequency will detect noise from a narrower band of frequencies in the same way and amplify the audible hiss.
The germanium diode detects audio frequencies in the noise and the audio appears across the resistor at the recorder cable input. This is an audible hiss that has spirit voices in it. The recorder records the audible sounds for future analysis and playback. I believe that natural noise created by ocean surf or rush of wind also can contain voices and electronics is not necessary to create them.
I have used the rush of current through a semiconductor junction to create the same random (white noise) sound. Voices or intelligence can be detected. No radio signals are needed in this case but voices still are present.
Joe