This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
This circuit uses unusual operational amplifiers, but equivalents can be tried. FETs can also be...
This circuit was obtained in a 1991 publication. What it does is to amplify a signal with unit...
This small digital transmitter uses a 1 MHz crystal, or another nearby frequency, to produce a...