Found on 80's Popular Electronics this circuit operates at 455 kHz. The explorer coil is formed by 10 turns of yarn 26 in a 4 inch shape. The indicator is a microammeter.
This circuit with an integrated circuit of the time was found in the magazine Radio Electronics of April...
This is a converter stage found in old transistor superheterodyne radios. The circuit is for...
In its original version of a 70s manual, this integrated amplifier, which is uncommon today, was...