4 - The Marconi Mk II Receiver - by Andrés Ramos

[Andres Ramos]

I already explained the good results I yielded with the coherer devices in the article Research Paper - EVP Reception with Coherers - Basic considerations by Andres Ramos. I decided to scrutinize this effect in more depth and took the graphite coherer as a starting point since it gave me the best voice signals and worked very stable. For my first experiments I used powdered carbon and the graphite powder from a hardware store. In my experiments I wanted to test more materials based on graphite.

My next step was to try graphite mines from a papershop. I arranged two of them with ductape on my working desk and fixed two wires to them. A third mine was losely lying across the other ones.

Graphite mine setup

The electrical contact over the mines was very weak as I wanted it to be. Via a series resistor I routed a small dc current through it with an adjustable voltage from my power supply. The gained results were of the same quality as with graphite powder. Sadly this setup was extremly susceptible for mechanical vibration. It was in fact a microphone!

From another project I made i knew another material based on graphite and that was conductive rubber. This is manufactured as small tubes of rubber with a certain amount of graphite mixed with the rubber. I also made a setup with these.

Conductive rubber setup

The setup was a lot more stable in mechanical terms and also slighly improved in signal quality. Moreover it was very easy to get it to emitt noise. I decided to design a complete receiver around this conductive rubber setup. For some marketing reasons it was coined the "Marconi Mk II" device.

The Marconi Mk II device

Sadly I don't have an electronic schematic anymore but the design was very much copied and pasted from the zincite receiver while replacing the zincite by a piece of conductive rubber with two electrodes. One with a screw only slightly touching the rubber. The receiver had knobs for rubber bias voltage, volume and also a microphone. By pressing the red button a red LED lights up and the voice of the experimenter is mixed with the noise stream while simultaneously muting the loudspeaker. This feature was implemented to record the questions of the experimenter along with the spirit signals.

See the attached test report for more details on the graphite coherer.

A collection of audio samples made with the Marconi device can be found here

 

Before finalizing this article i want to mention that I also ran an experiment that I called "Multifeeder". This was in fact a piece of rubber tube with more then one "cat whiskers" and a common electrode.

Multifeeder setup

I combined all the signals of the three feeders in a preamplifier. However whether the S/N ratio nor the overall signal quality was improved.

 

ITC report 2019-G-003.pdf