[regenfreak]

Here is a little fun circuit for the group delay equalizer. It works but produces very subtle improvement in the flatness of the group delay graph when it has been tested with 4 ceramic filter cascade with an IF amp. The loaded Q of the LC tank can be variable between Q=35 to 45 by adjusting the variable damping potentiometer. I have replaced the fixed 12K series resistor by lower or higher values, it makes little difference to the maximum Q. I dont know if I can improve it further by replacing the LC tank with a higher Q. Attached is the S21 and group delay in blue line. Note that although the group delay looks very flat in the graph, the vertical axis can be stretched or rescaled to exaggerate the distortion.

The Sansui patent for their group delay equalizer consisted of very complex LC network and it is not simple like this.