Found in a QST magazine from the 90s, this circuit broadcasts on different amateur radio bands depending on the coil. Data for the coil and crystal are provided next to the diagram.
This simple circuit uses a 200 µA galvanometer to measure voltages in three ranges. The circuit...
Today we can call this circuit a baby monitor. It is a microphone amplifier found in a publication by...
This circuit is from Motorola's Linear Interface ICs from 1993. The MC1723 is the equivalent of...