Operation Coherer

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the circuit of coherer receiver, recorded received code on morse paper tape recorder.


unlike modern radio stations transmit continuous radio frequency, amplitude (power) modulated audio signal, first radio transmitters transmitted information wireless telegraphy (radiotelegraphy), transmitter turned on , off (on-off keying) produce different length pulses of unmodulated carrier wave signal, dots , dashes , spelled out text messages in morse code. result, radio receiving apparatus merely had detect presence or absence of radio signal, not convert audio. device did called detector. coherer successful of many detector devices tried in days of radio.


the basis operation of coherer metal particles cohere (cling together) , conduct electricity better after being subjected radio frequency electricity. radio signal antenna applied directly across coherer s electrodes. when radio signal dot or dash came in, coherer become conductive. coherer s electrodes attached dc circuit powered battery created click sound in earphones or telegraph sounder, or mark on paper tape, record signal. unfortunately, reduction in coherer s electrical resistance persisted after radio signal removed. problem because coherer had ready receive next dot or dash . therefore, decoherer mechanism added tap coherer, mechanically disturbing particles reset high resistance state.


coherence of particles radio waves obscure phenomenon not understood today. recent experiments particle coherers seem have confirmed hypothesis particles cohere micro-weld phenomenon caused radio frequency electricity flowing across small contact area between particles. underlying principle of so-called imperfect contact coherers not understood, may involve kind of tunneling of charge carriers across imperfect junction between conductors.








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