Raudive Germanium Diode Receiver
Konstantin Raudive was, among other things, an EVP researcher in the 1960′s and 70′s, who devised a method of improving the quality of his EVP recordings.
Through experimentation he found that using a Germanium Diode plugged into a recorder instead of a microphone vastly helped improve the quality of the disembodied voices. We have found that the Germanium Crystal Diode is capable of picking up radio waves much like an old crystal radio set.
The circuit is essentially the same as the original and housed in an ABS plastic case. You can experiment by placing the unit in a Faraday Cage (a sealed, metal container) to ensure no outside contamination. But I find that it works best when used as it is and you will find that the diode will not pick up your own voice or any noise contamination from your recording area.
We highly recommend experimenting with this device.