Grid-leak Detector - Grid Leak Detector

Grid Leak Detector

The grid leak detector was in common use in the 1920s and 30s in radio receivers. The grid leak detector stage is a non-linear valve amplifier. The grid bias produced by the grid leak across the biassing grid leak resistor, plus the typically non-linear characteristic of the valves chosen, result in a non-linear rf amplifying stage. The stage performs two, or more often three functions:

• Detection: The nonlinearity of the stage produces an audio frequency detected component in the anode load.
• RF amplification: The stage is an RF amplifier as well as a detector, thus it gives much better sensitivity than a diode detector.
• Reaction: In most cases feedback was added to give reaction (aka regeneration) to boost RF sensitivity, selectivity and often output volume.

In simple one-valve sets, the grid leak detector drove the headphones, since it produced audio frequency output as well as radio frequency. In better sets, the grid leak detector's output fed an audio amplifying valve, or occasionally more than one.