This simple sensitive circuit was suggested in a July 1992 Radio Electronics issue. The relay is a double-contact changeover relay. Sensitivity adjustment is made at R2.
This circuit was found in a National Semiconductor manual that is now a Texas group company. The...
This switch or band selector for receivers was found in a Popular Electronics from the 1990s. The...
L1 is the secunday wound of a common power transformer with voltages between 6 and 12 V and...