This variable frequency circuit was found in a Popular Electronics from the 90s. The circuit outputs to a small speaker and can be powered by voltages as low as 3 V.
This amplified circuit was found in a magazine for radio amateurs 73 of the 90s. The circuit uses an...
We found this circuit in a 1980s publication on espionage. The transistors support modern...
This 6-transistor receiver was manufactured in Japan in the 60s. The circuit is superheterodyne and has a 6V...