Grid dip oscillator
ELECTRONIC INSTRUMENT THAT MEASURES THE RESONANT FREQUENCY OF NEARBY UNCONNECTED RADIO FREQUENCY TUNED CIRCUITS
Gate dip oscillator; Dip meter; Dipmeter; Grid dip meter
Grid dip oscillator (GDO), also called grid dip meter, gate dip meter, dip meter, or just dipper, is a type of electronic instrument that measures the resonant frequency of nearby unconnected radio frequency tuned circuits. It is a variable-frequency oscillator that circulates a small-amplitude signal through an exposed coil, whose electromagnetic field can interact with adjacent circuitry.