This circuit aims to increase the selectivity of receivers whose FI is 455 kHz. The circuit is from 1975 documentation. The transistors can be the modern BF494 equivalents.
The configuration presented below was obtained in the Linear Application Handbook of the National...
This small circuit for the medium or short-wave range, depending on the coil, was found in a...
In fact, the 556 consists of a double 555, which can be replaced by these integrated ones. The...