This circuit was found in Electronics Today International of the 80's. The circuit uses still common components, providing the indication through LEDs.
This S-meter circuit was found in a 1976 publication. The circuit is used to measure the signal...
The components of this filter are calculated using conventional formulas (see mathematics section of...
This is a Japanese commercial radio from the 60s. The superheterodyne circuit of 7 transistors for medium...