During this period the demodulator was usually a carborundum point contact diode, but sometimes a vacuum tube grid-leak detector.
2.
The first semiconductor devices, such as the 1N23 silicon point contact diode, were still designated in the old " RMA tube designation " system, where the " 1 " stood for " No filament / heater " and the " N " stood for " crystal rectifier ".
3.
Popcorn noise was first observed in early point contact diodes, then re-discovered during the commercialization of one of the first semiconductor op-amps; the 709 . No single source of popcorn noise is theorized to explain all occurrences, however the most commonly invoked cause is the random trapping and release of charge carriers at thin film interfaces or at defect sites in bulk semiconductor crystal.
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