Konstantin Raudive, was a Latvian writer and intellectual who spent a lifetime researching electronic voice phenomena (EVP). In 1971, he authored “Breakthrough: An Amazing Experiment in Electronic Communication with the Dead”, which is considered authoritative on the subject.
This hard to find book is the documented result of six years of scientific research into the phenomenon, accidentally discovered in Sweden in 1957 by the father of EVP, Friedrich Jorgenson. It includes transcripts of several EVP sessions along with a technical discussion on the methods used to generate the voices.
A flexi disk vinyl of the voice recordings was originally bundled with it. Here’s a link to the full audio for your listening pleasure. If you can manage to take off your pareidolia hat, it’s pretty amazing.
He describes four different approaches, but I find the “diode” method the most compelling as it’s supposed to capture the clearest voices. The book includes three different schematics below:
An excerpt from the book:
The diode method. A short (6-10 cm long) aerial is used to give a more or less broad-banded signal, which is rectified by a diode and fed directly by cable to the radio or microphone input of the tape-recorder.
This provides the clearest voices, but the interference caused by nearby strong wireless transmitters must be reckoned with.
In this day and age, “reckoning with wireless transmitters” sounds like a bit of a hopeless cause. Putting any doubts aside, I found with a quick search that there are more than a few schematics available for updated versions of this detector. I found the Raudive Diode Detector section from this link has a particularly nice write up and schematic. My plan is to build and test a device using this:
I’ll provide an update once I build the device. In the meanwhile, if you’ve captured EVPs, drop me a note and let me know about your hardware setup and experiences!