MASTER OSCILLATORIn a transmitter, the oscillator that establishes the carrier frequency of the
MASTER OSCILLATOR POWER AMPLIFIER (MOPA)A transmitter in which the oscillator is
isolated from the antenna by a power amplifier .
MATRIXIn computers, a logic network in the form of an array of input leads and output leads with logic
elements connected at some of their intersections .
MATTERAny physical entity that possesses mass .
MAXIMUM USABLE FREQUENCYMaximum frequency that can be used for communications
between two locations for a given time of day and a given angle of incidence .
MEASURE (METROLOGY AUTOMATED SYSTEM FOR UNIFORM RECALL AND
REPORTING)The Navy data processing system designed to provide a standardized system for the
recall, scheduling, and documenting of test equipment into calibration facilities .
MECHANICAL-ROTATION FREQUENCYThe speed in revolutions per minute of armatures in
electric motors and engine-driven generators; blade speed in turbines .
MECHANICAL SCANNINGThe reflector, its feed source, or the entire antenna is moved in a desired
MECHANIZATIONUsing electric or electro-mechanical switches to represent logic circuits (AND, OR,
NOT, NOR, NAND) .
MEDIUMThe vehicle through which a wave travels from one point to the next. Air, water, and wood are
MEDIUM ALTITUDE ORBITAn orbit from 2,000 to 12,000 miles above the earth. The rotation rate of
the earth and satellite are quite different, and the satellite moves quickly across the sky .
MEDIUM FREQUENCYThe band of frequencies from 300 kHz to 3 MHz .
MEGAA prefix meaning one million; also MEG .
MEGGERCommon name for a megohmmeter  .
MEGOHMMETERA meter that measures very large values of resistance; usually used to check for
insulation breakdown in wires .
METALLIC ARMORA protective covering for wires or cables. Made as a woven wire braid, metal
tape, or interlocking metal cover. Made from steel, copper, bronze, or aluminum .
METALLIC, INSULATORA shorted quarter-wave section of transmission line .
METALLIC RECTIFIERAlso known as a DRY-DISC RECTIFIER. A metal-to-semiconductor, large-
area, contact device in which a semiconductor is sandwiched between two metal plates. This
asymmetrical construction permits current to flow more readily in one direction than the other .
METAL-OXIDE SEMICONDUCTOR FIELD-EFFECT TRANSISTORSee MOSFET .
METERA device used to measure a specific quantity, such as current, voltage, or frequency .