U.S. Marine Corps Antenna Mcrp 6 22D Operating Instructions

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MCRP 6-22D
G
gain—The increase in signal strength that is produced by an ampli-
firer.
generator—A device that changes mechanical energy into electri-
cal energy.
ground—A very large semiconductive surface (the Earth) or a
smaller highly conductive surface.
ground radials—Wires on or in the earth to improve its conductiv-
ity near the antenna.
ground screen—A wire mesh ground plane.
ground wave—A radio wave that travels along the Earth’s surface
rather than through the upper atmosphere.
H
half-wave dipole antenna—A center-fed antenna whose electrical
length is half the wavelength of the transmitter or received signal.
half-wave vertical dipole antenna—A half-wave dipole con-
structed vertical to the Earth’s surface.
hertz—One cycle per second.
high frequency—frequencies between 3 and 30 MHz.
hop—A single reflection of the wave back to Earth at a point
beyond the horizon. 
						

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horizontal dipole—A dipole constructed parallel to the Earth’s sur-
face.
horizontal pattern—The horizontal cross-section of an antenna’s
three-dimensional radiation pattern.
horizontal polarization—Transmission of radio waves in such a
way that the electric lines of force are horizontal (parallel to the
Earth’s surface).
I
impedance—The total opposition offered by a circuit or compo-
nent to the flow of alternating current.
impedance match—The condition where the load impedance
equals the characteristic impedance of a transmission line.
inductance—The natural property of an electrical circuit which
opposes the rate of change or current, i.e., electrical “intertia.”
in phase—Two or more signals of the same frequency passing
through their maximum and minimum values of like polarity at the
same instant.
insulator—A device or material that has a high electrical resis-
tance; a nonconductor of electricity.
interference—A degradation of a received signal caused by
another transmitter, a noise source, or the desired signal propaga-
tion over two or more different routes.
inverted L antenna—A half-wave dipole fed by a one-quarter
wavelength long vertical section. 
						

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MCRP 6-22D
inverted vee antenna—A half-wave dipole erected in the form of
an upside-down vee, with the feed point at the apex. It is essentially
omnidirectional, and is sometimes called a “dropping doublet.”
ionization—The process where radiation and particles from the
Sun make some of the Earth’s atmosphere partially conductive.
ionosphere—A partially conducting region of the Earth’s atmo-
sphere between 50 kms and 400 kms high.
L
lambda—Greek lower case letter (l) used to represent a wave-
length with reference to electrical dimensions in antenna work.
linearly polarized antennas—Antennas that produce only one
polarization.
line of sight—The transmission path of a wave that travels directly
from the transmitting antenna to the receiving antenna. Also called
LOS.
load—A device that consumes electrical power.
loading—Providing or connecting an electrical device capable of
accepting power to match the impedance of an antenna to a trans-
mitter so that maximum power is radiated from a generating device,
such as a transmitter.
lobe—A bulge on an antenna radiation pattern which indicates the
direction in which radiated power is concentrated.
long-wire antenna—An end-fed single wire antenna usually one
wavelength or longer. 
						

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lowest usable frequency—The lowest frequency that will not be
absorbed by the ionosphere or smothered by atmospheric noise.
Also called LUF.
M
maximum usable frequency—The highest frequency for a given
elevation angle that will reflect from an ionospheric layer. Also
called MUF.
megahertz—One million cycles per second. Also called MHz.
modulate—To change the output of a transmitter in amplitude
phase, or frequency in accordance with the information to be trans-
mitted.
monopole antenna—An antenna with a single radiating element; a
whip antenna.
N
noise—Random pulses of electromagnetic energy generated by
lightning or electrical equipment.
O
offset angle—The angle at which a long wire antenna must be
aimed on either side of the direction to the base station.
omnidirectional antenna—An antenna whose radiation pattern
shows equal radiation in all horizontal directions.
oscillation—A periodic, repetitive motion or set of values (voltage,
current, velocity). 
						

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MCRP 6-22D
out of phase—Two alternating quantities not passing through cor-
responding values at the same time (e.g., if the current in a circuit
reaches its maximum value before or after the applied voltage does,
the current is out of phase with the voltage).
P
path loss—The ratio of received power to transmitted power.
polarization—The direction of the electric field of a radiated wave
relative to the surface of the Earth (vertical, horizontal, linear, and
circular).
polarization fading—Fading due to polarization rotation of a
received signal. The received signal decreases when the incoming
wave does not have the same polarization as the receiving antenna.
power gain—The directive gain of an antenna multiplied by its
efficiency
propagation—A phenomenon by which any wave moves from one
point to another; the travel of electromagnetic waves through space
of along a transmission line.
propagation path—The path or route over which power flows
from the transmitter to the receiver.
Q
quarter-wave antenna—An antenna with an electrical length that
is equal to one-quarter wavelength of the signal being transmitter or
received. 
						

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R
radiate—To transmit RF energy.
radiation—Energy that moves through space as electromagnetic
waves.
radiation patterns—A chart of relative radiation intensity (or
power) versus direction.
radio frequency—Any frequency of electrical energy capable of
propagation into space (usually above 20 kHz). Also called RF.
radio horizon—The greatest distance on the Earth at which a trans-
mitted wave can be received by the direct path from a transmitter
located on the Earth.
radio waves—Electromagnetic waves at a frequency lower than
3,000 GHz and propagated through space without and artificial
guide. 
receiver—Amplifying and selecting equipment that receives radio
frequencies and delivers a duplicate of the information impressed
on the transmitter.
reception—The process of recovering transmitted information; the
process of converting electromagnetic fields to current in wires.
reciprocity—The various properties of an anntenna apply equally
whether the antenna is transmitting or receiving.
reflected waves—Waves that change their direction of propagation
after striking a surface that is either a conductor or an insulator. 
						

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MCRP 6-22D
reflection—The turning back of a radio wave from an object or the
surface of the Earth.
reflector type antenna—An antenna placed in front of a conduct-
ing surface (reflector) for the purpose of increasing radiation in one
direction, at the expense of radiation in other directions.
refraction—The bending, or changing direction, of a radio wave
passing into or through layers of the atmosphere or the ionosphere
that have different density (dielectric constant).
refractive index—A measure of the degree by which the speed of
an electromagnetic wave is slowed as it propagates through a given
material.
resistance—The property of a material or substance to oppose the
passage of current through it, thus causing electrical energy to be
converted into heat energy.
resonance—The state or frequency of vibration, electrical or
mechanical, in which forces that impede the motion are minimum.
resonant length—The proper length of an antenna to render it reso-
nant
rhombic antenna—An antenna made of four wires of equal length
connected together in the shape of a rhombus.
S
scattering—The spreading or breaking up of electromagnetic
waves when they encounter objects of different electrical properties
than those in which the wave is traveling. 
						

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shortened dipole—A dipole antenna made to resonate at a lower
frequency by use of a coil.
signal—A radio wave that contains the transmitted message.
signal loss—The amount of signal power lost between the transmit-
ter and receiver.
signal-to-noise ratio—The power intensity of the signal compared
to that of the noise.
skip distance—The distances on the Earth’s surface between the
points where a radio wave sky wave leaves the antenna and is suc-
cessfully reflected and/or refracted back to Earth from the iono-
sphere.
skip zone—The space or region within the transmission range
where signals from a transmitter are not received, i.e., between the
ground wave and the point where the refracted wave returns.
sky wave—A radio wave that is reflected from the ionosphere.
sloping long-wire antenna—A wire antenna of length greater than
one wave-length and supported in an inclined orientation with
respect to the ground.
standing-wave ratio—The ratio of the maximum to minimum
amplitudes of voltage, or current, along a transmission line.
standing waves—Waves that appear not to be moving as the result
of power traveling in both directions along a transmission line.
stratosphere—The second layer of the Earth’s atmosphere, extend-
ing from 10 to 50 km. 
						

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MCRP 6-22D
sunspots—Activity on the Sun’s surface which is seen as a series of
blemishes that vary in size, number, and location.
T
take-off angle—The angle measured from the Earth’s surface or
horizontal up to the direction of propagation towards the iono-
sphere.
transistor—A minute electronic device that permits a small current
to control the flow of a larger current.
transmission line—A conductor that transfers radio frequency RF
energy from the transmitter to the antenna or from the antenna to
the receiver.
transmitter—A piece of equipment that generates and amplifies a
radio frequency, adds intelligence to this signal, and then sends it
out into the air as a radio frequency wave.
troposphere—The region of the Earth’s atmosphere from the sur-
face to a height of about 10 km.
tuning—The process of adjusting a radio circuit so that it resonates
at the desired frequency.
twin-lead transmission line—A balanced transmission line gener-
ally used with balanced antennas.
two element array—An antenna composed of two element anten-
nas. 
						

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U
ultrahigh frequency—Frequencies between 300 and 3,000 MHz.
unbalanced transmission line—A transmission line one of whose
conductors is grounded.
unidirectional—In one direction only.
V
vee antenna—Two long-wire antennas connected to form a vee.
velocity—The speed of a radio wave through the dielectric medium
it is in.
vertical dipole—A balanced or dipole antenna oriented vertically.
vertical polarization—Transmission of radio waves in such a way
that the electric lines of force are vertical (perpendicular to the
Earth’s surface).
vertical quarter-wave antenna—A monopole (whip) antenna that
is oriented vertically. 
very high frequency—  Frequencies between 30 and 300 MHz;
transmissions that follow the line of sight path.
voltage—Electrical pressure, expressed in volts, which is the result
of squeezing electrons together.
voltage standing-wave ratio—The ratio of the amplitude of the
electric field or voltage at a voltage maximum to that at an adjacent
voltage minimum. Also called VSWR.