This circuit uses the SQ3524, a switching integrated circuit. The circuit was found in the April 1991 issue of Radio Electronics magazine.
This circuit was found in a 1963 magazine, but can still be easily assembled with some current...
This circuit for signals around 4.5 MHz for old analog TV was found in the September 1992 Radio...
Found on an 80's Radio Electronics, this two-section circuit is designed to pass the frequency...