18WuD2x

deviation ratio In a frequency-modulated (FM)
signal, the ratio between the highest modulating
frequency and the maximum carrier deviation.
deviation sensitivity For a frequency-modulation
(FM) receiver, the smallest deviation that will prodetector
blocking • diagnosis 181
thereby causing the detector to oscillate at the
signal frequency.
detector circuit A demodulator circuit (i.e., one
used to recover the intelligence from a modulated
carrier).
detector probe See DEMODULATOR PROBE.
detector pull-in See DETECTOR BLOCKING.
detector stage In a receiver or instrument, the
separate stage that contains the detector circuit.
Some systems, such as a superheterodyne receiver,
have more than one detector. Also see
FIRST DETECTOR and SECOND DETECTOR.
detent A mechanical stop used on a rotary switch
to hold the switch pole securely in each selected
position.
detune 1. To adjust a circuit to some frequency
other than its resonant frequency. 2. To set the
frequency of a receiver or transmitter to some
point other than the frequency normally used. 3.
To stagger-tune a receiver intermediate-frequency
system.
detuning
Tuning to a point above or below the frequency
to which a device or system is normally
(or initially) adjusted (usually the resonant frequency
of the device).
detuning stub A device used for the purpose of
coupling a feed line to an antenna, while choking
off currents induced on the feed line as a result of
the near-field radiation of the antenna.
deupdating Producing an earlier form of a computer
file by substituting older records for current
ones.
deuterium Symbol, D, d, H 2 , or 2 H. Also called
heavy hydrogen. The hydrogen isotope having a
nucleus consisting of one proton and one neutron.
deuterium oxide Symbol, D 2 O. Also called heavy
water. This compound has wide use in nuclear
reactors.
deuteron The nucleus of a deuterium atom.
deuton See DEUTERON.
deutron See DEUTERON.
deviation 1. In a frequency-modulated (FM) radio
signal, the instantaneous amount of carrier frequency
shift away from the unmodulated frequency.
It is usually expressed in kilohertz;
directly proportional to the amplitude of the modulating
signal, up to a certain maximum that depends
on the bandwidth allowed. 2. The
maximum instantaneous carrier frequency shift
in a FM signal. 3. The extent or amount by which
a quantity drifts from its proper value.
deviation distortion In a frequency-modulation
(FM) receiver, distortion resulting chiefly from
discriminator nonlinearity and restricted bandwidth.
duce a specified audio output power. Expressed
in kilohertz, or as a percentage of rated deviation
of the receiver, measured with the receiver set for
maximum gain.
device 1. A simple or complex discrete electronic
component. 2. A subsystem used as a unit, and
regarded as a single component.
device complexity The number of components in
an integrated circuit.
device independence A characteristic of a computer,
that allows operation independent of the
types of input/output devices used.
dew point For a gas containing water vapor
(typically air), the highest temperature at which
the vapor condenses as the gas is cooled. The dew
point depends on the amount of vapor in the gas.
dew-point recorder An instrument for determining
and recording the temperature at which water
vapor in the air condenses to a liquid.
DF Abbreviation of DIRECTION FINDER.
DF antenna An antenna that is mechanically rotatable
or has an electrically rotatable response
pattern for use with a direction finder.
DF antenna system Two or more DF antennas arranged
for maximum directivity and maneuverability,
together with associated feeders and
couplers.
D flip-flop A delayed flip-flop. The state of the input
determines the state of the output during the
following pulse, rather than during the current
pulse.
dg Abbreviation of decigram.
dia Abbreviation of diameter.
diac
Instantaneous deviation (kHz)
A two-terminal, bilateral, three-layer semiconductor
device that exhibits negative resistance.
When the applied voltage exceeds a critical value,
the device conducts.
diagnosis
+6
+4
+2
0
−2
−4
−6
Deviation
= 5 kHz +−
deviation
Time
1. Determination of the cause and location
of a hardware malfunction. 2. In computer
operations, determination of the cause of a system
operation error.