Grid dip oscillators were first developed in the 1920s, and were built with vacuum tubes.

They also sold specialty test equipment for the ham radio market, including signal generators and grid dip oscillators.

Modern grid dip oscillators are solid-state devices and are more versatile.

Grid dip oscillator, a radio frequency measuring instrument.

Grid dip oscillators have been widely used by amateur radio operators for measuring the properties of resonant circuits, filters, and antennas.

Grid dip oscillator (GDO), also called grid dip meter, dip meter, dipmeter, or just dipper, is a measuring instrument to measure resonant frequency of radio frequency circuits.

Solid-state versions of the grid dip oscillator are sometimes called gate dip oscillators or emitter dip oscillators in reference to the parts of the semiconductor whose current is being measured instead of the grid current on a vacuum tube.

Since the transmitter only covered 3.5 mHz and higher, it a new set of plug-in coils with the aid of Schneider's Millen grid dip meter.

Grid dip oscillator (GDO), also called grid dip meter, dip meter, dipmeter, or just dipper, is a measuring instrument to measure resonant frequency of radio frequency circuits.