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

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MCRP 6-22D
ranges are assigned to many activities, including citizens (public)
communications (e.g., mobile, police, weather, taxis, and general
purpose).
POLARIZATION
In many countries, FM and TV broadcasting in the VHF range use
horizontal polarization. One reason is because it reduces ignition
interference, which is mainly vertically polarized. Mobile commu-
nications often use vertical polarization for two reasons. First, the
vehicle antenna installation has...

Antenna Handbook ______________________________ 
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At frequencies below 30 MHz, system sensitivity is almost always
limited by receiver noise rather than by noise external to the
antenna (e.g., atmospheric and manmade interference). Generally,
wider modulation or signal bandwidths are employed in VHF and
UHF transmissions than at HF. Since system noise power is directly
proportional to bandwidth, additional antenna gain is necessary to
preserve a usable S/N ratio.
VHF and UHF antenna directivity (gain)...

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MCRP 6-22D
short enough that it is possible to construct resonant antenna arrays.
An array provides directivity (the ability to concentrate radiated
energy into a beam that can be aimed at the intended receiver).
Arrays of resonant elements, (e.g., half-wave dipoles), can be con-
structed of rigid metal rods or tubing or of aluminum or copper foil
laid out or pasted on a flat nonconducting surface. Directing power
helps to increase the range of the...

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RADIATORS
A radiator is the antenna component that transmits RF energy.
Vertical Radiator
A vertical radiator for general coverage use at UHF should be one-
quarter wavelength long. Longer vertical antennas do not have their
maximum radiation at right angles to the line of the radiator. They
are not practical for use where the greatest possible radiation paral-
lel to the Earth is desired. It is important that the antenna be decou-
pled from the...

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MCRP 6-22D
antennas operating at frequencies above 100 MHz. Ordinary wood
is a good example. In minimal rainfall climates, using very dry red-
wood, maple, or fir boiled in paraffin wax for several hours is fairly
successful up to frequencies as high as 560 MHz. The neck of a
glass soft drink bottle or other similar items work reasonably well
up to frequencies as high as 1 GHz. Several modern plastics, used
throughout the world, also make excellent insulators...

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to use relay stations or carefully placed reflectors when obstacles
interfere with the direct path.
When operating from areas where the transmission path is bounded
rather closely by reflective objects (e.g., buildings or metal towers)
the possibility of multipath exists. Whenever conditions are such
that radio signals travel two or more separate paths from the trans-
mitting to the receiving antenna, a phenomenon known as an inter-
ference pattern is...

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MCRP 6-22D
Vegetated Areas
VHF and UHF communications through a dense forest over dis-
tances of more than a few kilometers can often be very difficult. In
many tropical regions, trees and underbrush absorb VHF and UHF
radio energy. In addition to the ordinary free space loss between
transmitting and receiving antennas, a radio wave passing through a
forest undergoes an additional loss that is measured in dBs per km.
This extra loss increases rapidly as the...

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exceeding 30 kms, it may be necessary to use high-angle iono-
spheric propagation in the 3 to 10 MHz frequency range (i.e., HF)
to obtain a reliable circuit.
ANTENNA TYPES
The vertical whip is the most commonly used antenna. The OE-254
is a broadband, omnidirectional, biconical antenna. Antennas
located in places which are enclosed mostly in a metal shell or con-
tainer (e.g., an automobile) cannot be expected to perform as well
as if located outside...

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MCRP 6-22D
reflector reflects some of the radio energy back towards the whip
and provides a broad beam of energy towards the distant station.
Characteristics are—
Frequency range:30 to 88 MHz
Polarization:Vertical
Power capability:Matched to specific radio
Radiation pattern
Azimuthal (bearing):
Vertical (take-off angle):
OE-254
The OE-254 (fig. 5-1) is scheduled to replace the RC-292. Unlike
the RC-292, the OE-254 does not require tuning for specific bands
and...

Antenna Handbook ____________________________ 
5-11Figure 5-1. Installed OE-254 Antenna.