We found this circuit in a 90s Popular Electronics. The circuit uses a pickup coil that consists of 100 to 200 turns of wire 28 around the cable to be monitored.
This 1987 signal injector included the power supply from the power grid. The transformer is 6 + 6...
This amplifier was found in a 70s documentation. The product gain x bandwidth is 350 MHz. The...
This simple receiver with junction FET uses a high impedance magnetic earphone (over 2 k). Power...