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Author Topic: How do crystal electrical generators work?  (Read 12939 times)

Offline teragram

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Re: How do crystal electrical generators work?
« Reply #25 on: 13/01/2016 17:34:24 »
Pardon me for butting in:-

I understand that the "crystal" in a crystal radio is actually the detector (originally "cat's whisker"). To restate the obvious, radio frequency energy is collected by the aerial, the required frequency is selected by the tuning coil and a capacitor, either of which can be variable to select a particular broadcast. The received signal is of course a sine wave at high frequency, well outside audible frequencies. A broadcast signal carries information by modulation of the sine wave (carrier). The function of the crystal (diode) is purely to rectify the sine wave, as does any single diode, by removing (say) the negative halves. This "demodulation" process allows the signal carried by the sine wave to be heard via a very sensitive earpiece. As far as I know the crystal collects no energy at all, merely rectifies the carrier sine wave.
Any comments correcting the above would be welcomed as attempts to improve my understanding.
Without doubt though, the references to the carbon microphone as an energy collector are misleading, as the device is merely a variable resistor responding to audio sound pressure changes, and must be used in series with a battery or other DC supply. Therefore the energy involved is supplied by the current source, not the microphone.
 
 

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Re: How do crystal electrical generators work?
« Reply #25 on: 13/01/2016 17:34:24 »

 

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