MAGIC-T JUNCTION—A combination of the
H-type and E-type T-junctions.
MAGNETIC FIELD—See H-FIELD.
MAJOR LOBE—The lobe in which the greatest
amount of radiation occurs.
MARCONI ANTENNA—A quarter-wave antenna
oriented perpendicular to the earth and operated
with one end grounded.
Also known as
QUARTER-WAVE ANTENNA.
MAXIMUM USABLE FREQUENCY—Maximum
frequency that can be used for communications
between two locations for a given time of day
and a given angle of incidence.
MEDIUM—The substance through which a wave
travels from one point to the next. Air, water,
wood, etc., are examples of a medium.
METALLIC INSULATOR—A shorted quarter-wave
section of transmission line.
MICROWAVE REGION—The portion of the
electromagnetic spectrum from 1,000 megahertz
to 100,000 megahertz.
MINOR LOBE—The lobe in which the radiation
intensity is less than a major lobe.
MULTIELEMENT ARRAY—An array consisting
of one or more arrays and classified as to
directivity.
MULTIELEMENT PARASITIC ARRAY—An array
that contains two or more parasitic elements and
a driven element.
MULTIPATH—The multiple paths a radio wave may
follow between transmitter and receiver.
NEGATIVE ALTERNATION—The portion of a
sine wave below the reference line.
NODE—The fixed minimum points of voltage or
current on a standing wave or antenna.
NONDIRECTIONAL—See OMNIDIRECTIONAL,
NONRESONANT LINE—A transmission line that
has no standing waves of current or voltage.
NORMAL—The imaginary line perpendicular to the
point at which the incident wave strikes the
reflecting surface. Also called the perpendicular.
NULL—On a polar-coordinate graph, the area that
represents minimum or 0 radiation.
OMNIDIRECTIONAL—Transmitting in all direc-
tions. Also known as NONDIRECTIONAL.
OPEN-ENDED LINE—A transmission line that has
an infinitely large terminating impedance.
OPTIMUM WORKING FREQUENCY—The most
practical operating frequency that can be used
with the least amount of problems; roughly 85
percent of the maximum usable frequency.
ORIGIN—The point on a graph where the vertical
and horizontal axes cross each other.
OUTPUT END—The end of a transmission line that
is opposite the source. Also known as RECEIV-
ING END.
OUTPUT IMPEDANCE—The impedance presented
to the load by the transmission line and its source.
PARALLEL RESONANT CIRCUIT—A circuit that
acts as a high impedance at resonance.
PARALLEL-WIRE—A type of transmission line
consisting of two parallel wires.
PARASITIC ARRAY—An array that has one or
more parasitic elements.
PARASITIC ELEMENT—The passive element of
an antenna array that is connected to neither the
transmission line nor the driven element.
PERIOD—The amount of time required for comple-
tion of one full cycle.
AI-6
