Marconi Magnetic Detector

Marconi Magnetic Detector


   These photos were grabbed from an eBay listing in October 2017. While it does show the mechanism of a Marconi detector, I suspect the device has been remounted on a new 'chassis'. Any radio device from 100 years ago would be built on polished lacquered wood or Bakelite and have manufacturer's nameplate affixed.
   The continuous loop of wire has been replaced by string for appearances sake. This originally consisted of a bundle of fine soft iron wires, insulated with silk. The clock work mechanism would move the wire at a rate of 7-8 cm/sec. There are two coils, one wound on top of the other. The antenna and ground would be connected to one coil and the earphones would be connected across the second. Any electromagnetic disturbance impinging on the antenna wire would induce a current into the coil, which in turn magnetizes the wire. The antenna coil is wound on a glass tube and is closest to the wire. The earphone coil is larger is diameter and is centered on the antenna coil--easily seen in the photos. The buzz of the spark transmitter would be clearly heard. The magnet served to 'erase' the wire.
   Later in life, this detector would have a Marconi Tuner placed between it and the antenna. This would improve the receiving station by providing some selectivity and antenna resonating. Sensitivity of the whole apparatus depended on the quality of the ear-phones used.
   Click on the photos for an enlarged view.


   General view. Clockwork on the right, idler on the left, antenna and earphone coil in the centre.

   This fan provided some drag on the mechanism to control the wire's speed.

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