This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from an approaching storm. The circuit was taken from a Popular Electronics from the 90s.
This 6V microsupply with just 2mA current uses a common 1N34 germanium diode. The circuit was...
This circuit for a frequency of 100 kHz was found in documentation from the 60's. The circuit can...
This preamplifier for record players with crystal capsules was found in Radio Electronics magazine...