AI-4
MASTER OSCILLATOR POWER AMPLIFIER (MOPA)—A transmitter in which the
oscillator is isolated from the antenna by a power amplifier.
MICROPHONE—An energy converter that changes sound energy into electrical energy.
MODULATED WAVE—A complex wave consisting of a carrier and a modulating wave that is
transmitted through space.
MODULATING WAVE—An information wave representing intelligence.
MODULATION FACTOR (M)—An indication of relative magnitudes of the rf carrier and the
audio-modulating signal.
MODULATION INDEX—The ratio of frequency deviation to the frequency of the modulating
signal.
MODULATION—The ability to impress intelligence upon a transmission medium, such as radio
waves.
MODULATOR—The last audio stage in which intelligence is applied to the rf stage to modulate
the carrier.
MULTIPLICATION FACTOR—The number of times an input frequency is multiplied.
MULTIVIBRATOR MODULATOR—An astable multivibrator used to provide frequency
modulation by inserting the modulating af voltage in series with the base-return of the
multivibrator transistors.
NEGATIVE ALTERNATION—That part of a sine wave that is below the reference level.
NONLINEAR DEVICE—A device in which the output does not rise and fall directly with the
input.
NONLINEAR IMPEDANCE—An impedance in which the resulting current through the device
is not proportional to the applied voltage.
OVERMODULATION—A condition that exists when the peaks of the modulating signal are
limited.
PEAK AMPLITUDE—The maximum value above or below the reference line.
PEAK DETECTION—Detection that uses the amplitude of pam or the duration of pdm to
charge a holding capacitor and restore the original waveform.
PEAK POWER—The maximum value of the transmitted pulse.
PERCENT OF MODULATION—The degree of modulation defined in terms of the maximum
permissible amount of modulation.
PERIOD—The duration of a waveform.
PHASE MODULATION (pm)—Angle modulation in which the phase of the carrier is
controlled by the modulating waveform. The amplitude of the modulating wave determines
the amount of phase shift and the frequency of the modulation determines how often the
phase shifts.
