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.
In this circuit the capacitor under test is charged at switch position A and then discharged...
This is a common circuit in the 1990s, when experimental FM transmitters were in vogue. The...
Using a piezoelectric sensor of the time, this circuit was found in the February 1994 issue of...