18WuD2x

450 minor lobe • mixture
relative to the main lobe. Also see MAIN LOBE,
SIDE LOBE.
minor loop A subordinate path for the circulation
of information or control signals in an electronic
system (e.g., minor feedback loop). Compare MA-
JOR LOOP.
minute 1. Abbreviation, min. A unit of measure of
time equal to 60 seconds or 1 ⁄60 hour. 2. Also called
minute of arc. Symbol (‘). A unit of arc measure
equal to 1 ⁄60 angular degree or 60 seconds. 3. General
term meaning “extremely small.”
MIR Abbreviation of memory-information register.
mirror 1. A device consisting chiefly of a highly
polished or silvered surface that reflects a large
part of the radiation (such as light) striking it.
2. Radar-interference material (see CHAFF). 3. To
reflect, as by a mirror.
mirror galvanometer A galvanometer in which a
mirror is moved by the coil. The mirror either reflects
a spot of light along an external scale, or it
reflects the scale, which is then read through a
small telescope.
mirror-galvanometer oscillograph See ELEC-
TROMECHANICAL OSCILLOSCOPE.
mirror image 1. An image or curve that is exactly
reversed relative to a straight line or flat plane,
compared to a reference image or curve. Compare
BILATERAL SYMMETRY. 2. For a quarter-wave
Marconi antenna, the extra quarter-wave element
supplied by the earth. 3. For an antenna at a distance
d above a ground plane, an effective antenna
at an equal distance d below the ground
plane.
Antenna
Image
λ/4
λ/4
mirror image, 2
Ground
mirror-reflection echo A false radar echo or set of
echoes, caused by reflection of the radar beam
from a plane surface prior to its encountering the
target or targets. The beam can also be reflected
from one target to another.
mirror-type meter A meter whose movable coil
carries a small mirror (rather than a pointer) that
reflects a beam of light to produce a spot on a
translucent scale.
misaligned head In a tape recorder, a record or a
pickup head that is incorrectly oriented, with respect
to the passing tape.
misfire Failure of a gas tube or mercury-arc tube
to ignite at the correct instant.
misleading precision In electronic calculations
and data recording, greater precision than the instruments
or conditions justify. Also see SIGNIF-
ICANT FIGURES.
mismatch The condition resulting from joining two
circuits, or connecting a line to a circuit, in which
the impedances are substantially different.
mismatched impedances Impedances that are
unequal, and thus do not satisfy the conditions
for maximum power transfer.
mismatch factor For a load not perfectly matched
to a driving circuit, the ratio of current flowing in
the load to the current that would flow in the load
if its impedance were perfectly matched to the
output impedance of the driving circuit.
mismatch loss For a load that is mismatched to a
source, the ratio P 1 /P 2 , where P 1 is the power a
matched load would absorb from the source, and
P 2 is the power actually absorbed by the mismatched
load.
mistor A variable-resistance device, used to detect
the presence of a magnetic field and to measure
magnetic-field strength.
MIT Abbreviation of MASTER INSTRUCTION TAPE.
mix 1. To produce a beat signal (either the sum or
the difference frequency) from two input signals.
2. The proportion of powdered iron and other inert
substances in a ferromagnetic transformer
core. Different mixes result in different operating
characteristics.
mixdown A method of combining recorded sound
from two or more audio tracks, and recording the
result onto an audio tape or disc. It is used to create
special audio effects.
mixed-base notation A number system in which
the base (radix) alternates between two digit positions.
Also called mixed radix notation.
mixed calculation A mathematical calculation or
expression in which more than one operation is
used.
mixed modulation Modulation of several kinds coexisting
in a system. Thus, a small amount of undesired
frequency modulation might accompany
amplitude modulation, or vice versa.
mixed number A number having integral (whole)
and fractional parts (e.g., 3.14159).
mixer 1. A device, such as a transistor or semiconductor
diode, used to mix two input signals and
deliver an output equal to their difference and/or
sum (see MIXING). 2. See AUDIO MIXER. 3. Any
device that combines two or more signals, yielding
one output signal whose nature is determined
by the characteristics of the circuit.
mixer noise Electrical noise that occurs in a
MIXER.
mixing Combining several signals so that some desired
mixture of the original signals is obtained.
Compare MODULATION.
mixture 1. A combination of two or more signals
that retain their characteristics—even when they
interact to produce beat-frequency products. 2. A