Grid dip oscillator

A dipmeter, also called Grid dipper is a device for measuring the resonant frequency of the electrical resonant circuits, or antennas. It comprises a tunable oscillator with a coil, which is accessible from the outside. The measuring range is typically between 0.1 MHz and 500 MHz and can be selected in coarse steps by replacing the coil ( coil plug ).

Metrics of a Dipmeters are often resonant circuits, as used for example for IF, oscillator and tuning circuits in RF receivers, transmitters, measuring and test equipment. They consist of a coil and a low-loss capacitor. Often, the dipmeter can also be used as a selective measurement receiver.

The term has been coined as the active element of the oscillator was previously an electron tube, the grid current (English " grid" ) was measured. At the resonance frequency of the measuring instrument shows a characteristic decrease (English " dip" ) the grid current.

Action principle

When two resonant circuits (weak) are coupled because penetrate for example, the magnetic fields of their coils each other, they exchange among themselves power from: The active circuit ( ie the oscillator ) loses power, which converts the passive resonant circuit in either heat or radiates. This power loss is at resonance of the two circles at the largest and most can (English: grid dip) at the " tuning " as a waste of the grid current to be measured or the base or gate current of the oscillator. The stronger the coupling between the oscillator and absorber circuit, the more pronounced, but also " broad " is the dip. At resonance, the damping of the oscillator circuit through the object being measured at the largest and its depression is at its lowest. However, since the tuning is done by hand, the accuracy of the frequency measurement is limited to a few percent. An additional connected frequency counter can therefore only increase the reading accuracy of the Dipmeters compared to a similar frequency scale.

Construction

The picture shows the main components of a typical Dipmeters. The air coil, plugged bottom left of the device, which in this ( top ) range around 200 MHz of only one turn. The variable capacitor tunes the oscillator frequency of the Dipmeters. He can be seen on the right edge in its bright, transparent plastic cover. The disc for the adjustment of the capacitor on the bottom serves as a scale for reading off the measurement frequency. The rash of small moving coil instrument in the upper section of the image varies with the transmission power.

Modes

• Active: When measuring transmitter, in this case the measuring arrangement is such as a passive resonant circuit or antenna through the built-in oscillator is excited, and the "loss " in resonance at the frequency set on the dipmeter determined qualitatively. Here, a frequency meter could also measure the transmission frequency of the Dipmeters directly. This is the " normal" mode of Dipmeters.

• Passive: In this case the to be measured resonant circuit itself must radiate power. To the resonant circuit of the Dipmeters is not operated in an oscillator circuit, but also serves as an input filter in the measuring receiver ( Einkreisempfänger ). After this input filter was tuned manually to maximum reception (dip ), the deflection of the pointer instrument shows the relative strength of the transmitted signal and the tuning scale whose frequency ( absorption rate monitor ). In some devices, a headphone for monitoring the modulation can be connected.