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FREE-SPACE LOSS—The loss of energy of radio waves caused by the spreading of the wavefront as it
travels from the transmitter [10].
FREQUENCY (f)—(1) The number of complete cycles per second existing in any form of wave motion,
such as the number of cycles per second of an alternating current [2] [10]. (2) The rate at which the
vector that generates a sine wave rotates [12].
FREQUENCY COMPENSATION NETWORK—Circuit modification used to improve or broaden the
linearity of its frequency response [18].
FREQUENCY CUTOFF—The frequency at which the filter circuit changes from an action of rejecting the
unwanted frequencies to an action of passing the desired frequencies. Conversely, the point at which the
filter circuit changes from an action in which it passes the desired frequencies to an action in which it
rejects the undesired frequencies [9].
FREQUENCY-DETERMINING NETWORK—A circuit that provides the desired response (maximum
or minimum impedance) at a specific frequency [8].
FREQUENCY DEVIATION—The amount the frequency varies from the carrier frequency [12].
FREQUENCY DIVERSITY—Transmitting (and receiving) of radio waves on two different frequencies
simultaneously [10].
FREQUENCY-DIVISION MULTIPLEXING—Multiplexing that transmits and receives the full 360
degrees of each sine wave [17].
FREQUENCY METER—A meter used to measure the frequency of an ac signal [3] [16].
FREQUENCY MODULATION (fm)—Angle modulation in which the modulating signal causes the
carrier frequency to vary. The amplitude of the modulating signal determines how far the frequency
changes, and the frequency of the modulating signal determines how fast the frequency changes [12].
FREQUENCY MULTIPLIERS—Special RF power amplifiers that multiply the input frequency [12].
FREQUENCY RESPONSE—The measure of a servo's ability to respond to various input frequencies [15].
FREQUENCY-RESPONSE CURVE—A curve showing the output of an amplifier (or any other device)
in terms of voltage or current plotted against frequency with a fixed-amplitude input signal [8].
FREQUENCY SCANNING—Varying the output frequency to achieve electronic scanning [18].
FREQUENCY-SHIFT KEYING (fsk)—Frequency modulation somewhat similar to continuous-wave
(cw) keying in AM transmitters. The carrier is shifted between two differing frequencies by opening
and closing a key [12].
FREQUENCY SPECTRUM—In a radar, the entire range of frequencies contained in an RF pulse or signal
[18].
FREQUENCY STABILITY—Refers to the ability of an oscillator to accurately maintain its operating
frequency [9].
FREQUENCY SYNTHESIS—A process that uses hetrodyning and frequency selection to produce a signal
[17].
