We found this circuit in an 80's Electronic Design. It makes use of couplers of the time that can be replaced with equivalents.
This filter was found in the October 1969 issue of Radio Electronics magazine. The frequency...
The circuit in the figure has the same purpose as the previous one (CBV15991E), except that it has a...
Found in a Popular Electronics from the 90s, this circuit can be adapted to use LEDs. The power...