Found in a Popular Electronics from the 90s, this circuit is intended to measure the harmonic distortion of an audio signal. The circuit can be tuned between 970 and 1030 Hz.
This circuit is from a publication from the 50's. Inductive components are critical, and...
This simple two-transistor circuit used transistors from the 60s, having been found in a...
This circuit uses an oscillator that generates a signal of approximately 1450 kHz to test...