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A frequency at which the attenuation of a device begins to increase sharply, such as the limiting frequency below which a traveling wave in a given mode cannot be maintained in a waveguide, or the frequency above which an electron tube loses efficiency rapidly. Also known as critical frequency; cutoff.



Related Terms

MAGNETRON

An electron tube characterized by the interaction of electrons with the electric field of circuit element in crossed steady electric and magnetic fields to produce an alternating current power output. It is used to generate high power output in the ultra-high and super-high frequency bands.

ATTENUATION

  1. A lessening in amount, particularly the reduction of the amplitude of a wave with distance from the origin. 2. The decrease in the strength of a radar wave resulting from absorption, scattering, and reflection by the medium through which it passes (wave guide, atmosphere) and by obstructions in its path. Also attenuation of the wave may be the result of artificial means, such as the inclusion of an attenuator in the circuitry or by placing an absorbing device in the path of the wave.

ELECTRON HOLOGRAPHY

An imaging technique using the wave nature of electrons and light, in which an interference pattern between an object wave and a reference wave is formed using a coherent field-emission electron beam from a sharp tungsten needle, and is recorded on film as a hologram, and the image of the original object is then reconstructed by iilluminating a light beam equivalent to the reference wave onto the hologram.

JOYSTICK

A two-axis displacement control operated by a lever or ball, for XY positioning of a device or an electron beam.

CHRONOCYCLEGRAPH

A device used in micromotion studies to record a complete work cycle by taking still pictures with long exposures, the motion paths being traced by small electric lamps fastened to the worker's hands or fingers; time is obtained by interrupting the light circuits with a controlled frequency which produces dots on the film.

ANODE CURRENT

The electron current flowing through an electron tube from the cathode to the anode. Also known as plate current.

AUTOMATIC FREQUENCY CONTROL

The technique of automatically maintain- ing, or a circuit or device which automatically maintains, the frequency of a receiver within specified limits.

FREQUENCY MODULATION

Angle modulation of a sinewave carrier in which the instantaneous frequency of the modulated wave differs from the carrier frequency by an amount proportional to the instantaneous value of the modulating.

OUTPUT-METER ADAPTER

Device that can be slipped over the plate prong of the output tube 385 output-meter adapter output power of a radio receiver to provide a conventional terminal to which an output meter can be connected during alignment.

FREQUENCY-RESPONSE CURVE

A graph showing the magnitude or the phase of the freqency response of a device or system as a function 235 frequency-response curve frequency-response trajectory of frequency. Also known as frequency characteristic. frequency spectrum

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