This crystal tester was found on a 90s Ham Radio. Transistors are commonly used. The circuit is for testing crystals from 2 to 20 MHz.
The circuit shown in the figure generates a rectangular signal whose frequency depends on C1. For...
This circuit suggested by Texas Instruments, operates with pulses, and is based on an operational...
This circuit captures, through a coil, the signals emitted by another coil under the mat connected to...