Regenerative Receivers

Posted on Feb 5, 2014

This page covers several different regenerative receiver circuits that were used in the past, mostly from 1920s to 1940s. Connections are shown with electron tubes (vacuum tubes/valves), but FET transistors can be substituted with little or no changes. To those infected with radio bug, this page might be a useful resource. It shows different conne

Regenerative Receivers
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ction setups for tube based regenerative receivers. As such they might prove useful for new tube builds or FET/bipolar transistor implementations. Throughout, L1 is antenna coil, L2 main coil and L3 feedback "tickler" coil. Headphones H can be replaced with audio transformer or suitable RC combination for connection to next amplifier stage, in all circuits. R1 is around 1 megaOhm, C2 around 100 picoFarads. 1. Classic connection - plain inductive reaction. High frequency radio signal is coupled from antenna coil L1 to main tank circuit L2 - C1 used to select radio station. Triode is connected as grid demodulator (audion). Demodulated audio signal at anode is sent to headphones H. Positive feedback is achieved with tickler coil L3, feeding back part of high frequency energy from anode to grid circuit (coil L2). Regulation of positive feedback is done by change of L2 <-> L3 distance, or by L3 rotation. Coils L2 and L3 must have proper "polarity". If they are wound in the same direction (say clockwise on coil form) they should be connected as indicated on schematic. If positive feedback cannot be achieved, try swapping L3 ends. If it still doesn`t work, L3 is too far away from L2, or it has insufficient number of turns. For medium wave 540 - 1600 kHz reception, L1 should have about 5-10 turns, L2 around 80, and L3 40-50 turns of insulated or lacquered copper wire on cylinder with 30 mm diameter. If ferrite is used instead of...

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