This circuit for the 60 kHz range was found in 73 magazine and published in 1995. The circuit uses a ferrite rod. Note the direction of the coil windings.
This cricket circuit obtained in a 1992 documentation has an amplifying stage that, however, takes...
This circuit was found in a 1980s English publication, but can still be easily assembled by the...
This circuit is from old documentation, but can be adapted to use modern components. Power...