Originally designed for WWV (Standard Time Station) signals, it lets 1 kHz tones pass by rejecting the 440 and 600 Hz tones emitted by the station. The circuit is from a 1964 Electronic Design.
This signal follower, from a publication from the 1970s, uses old germanium transistors such as...
Although it is a common configuration today, this circuit was taken from an old publication. The...
This circuit for the 85 to 95 MHz band has a gain of 15 dB. We find it in a 1980s documentation. The...