Suggested by a 90s Popular Electronics this circuit is intended to receive volleys or whistles from thunderstorms in the wave range below 20 kHz. The coil consists of 300 turns of wire 26 in a ferrite rod.
Using the name of varactor this circuit was found in the Radio Electronics magazine of July 1982....
In the figure we have a differentiator with the LM3900 transconductance amplifier. The circuit is...
This is one of the many approaches we have on the site for this low power 0.5 W amp using the...