This unusual circuit from a Popular Electronics of the 90s uses LED indicators, operating as a bridge. The components used are common. It is based on the tuning of the signal by a PLL.
This circuit is a variation of the common grid dip meter, having been found in a 1975 publication on FETs....
This circuit was found in old documentation, but the setting applies to any operational. Resistors...
This circuit was found in an Electronics World magazine from 1990. The circuit can be mounted...