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

Antenna Handbook ______________________________ 
4-5
After selecting the antenna, determine how to feed the power from
the radio to the antenna (fig. 4-1). Most tactical antennas are fed
with coaxial cable (RG-213). Coaxial cable is a reasonable compro-
mise of efficiency, convenience, and durability. Issued antennas
include the necessary connectors for coaxial cable or for direct con-
nection to the radio. 
Figure 4-1. Antenna Feed Lines.
Problems may arise in connecting field expedient antennas. The...

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MCRP 6-22D
antenna as a choke (see fig. 4-2). Connect the cable’s center wire to
one leg of the dipole and the cable braid to the other antenna leg.
Form the coaxial cable into a 6-inch coil (consisting of ten turns),
and tape it to the antenna under the insulator for support. 
  DETERMINING ANTENNA GAIN
Determine antenna gain at a specific take-off angle from the vertical
radiation pattern. Figure 4-3 shows the vertical antenna pattern for
the 32-foot vertical...

Antenna Handbook ______________________________ 
4-7
pattern line. Move down to the bottom scale. The gain is a little less
than 2.5 dBi (the line between 0 and 5 dBi). The gain of the 32-foot
vertical whip at 9 MHz and 20° is 2 dBi.
Once the antenna’s overall characteristics are determined, use the
antenna selection matrix (table 4-3 on page 4-8) to find the specific
antenna for a circuit. If the proposed circuit requires a short-range,
omnidirectional, wideband antenna, the selection matrix shows that...

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MCRP 6-22D
the 100-foot vertical half-rhombic antenna is the best choice because
it provides the highest gain at the required take-off angle.  
ANTENNA TYPES
The AS-2259/GR, vertical whip, half-wave dipole, inverted vee,
long wire, inverted L, sloping vee, sloping wire, and vertical half-
rhombic antennas are described and illustrated.Table 4-3. Antenna Selection Matrix.
UseDirectivityPolar-
izationBand-
width
Sky WaveGround Wave
Short (500 Miles)
Medium (500 to...

Antenna Handbook ______________________________ 
4-9
AS-2259/GR
The AS-2259/GR antenna (fig. 4-4)  provides NVIS propagation for
short-range radio circuits. It consists of two crossed sloping dipoles
positioned at right angles to each other and is supported at the center
by a 15-foot mast.  In use, the dipole’s components provide guying
support for the mast. Characteristics are—
Frequency range:2 to 30 MHz
Polarization:Horizontal and vertical simultaneously
Power capability:1,000 watts
Radiation pattern...

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MCRP 6-22D
 
Figure 4-5. AS-2259 Vertical Radiation Pattern.
Vertical Whip
The vertical whip is a component of all Marine Corps radio sets
(see fig. 4-6). It is available and easy to use on almost all radio cir-
cuits; however, it is probably the worst antenna to use on sky wave
circuits. Unless the radio circuit involves omnidirectional ground
wave propagation, any other antenna would provide better commu-
nications. For example, vertical whips are often used...

Antenna Handbook ____________________________ 
4-11
4-7 on page 4-12, 4-8 on page 4-13, and 4-3 on page 4-7 illustrate
various vertical whip antenna patterns.
Characteristics are—
Frequency range:2 to 30 MHz
Polarization:Vertical
Power capability:Matched to specific radio
Radiation pattern
Azimuthal (bearing):Omnidirectional
Vertical (take-off angle):See figures 4-7 on page 4-12, 4-8 on 
page 4-13, and 4-3 on page 4-7
Figure 4-6. Vertical Whip with Reflector.
If a vertical whip must be used, there are...

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MCRP 6-22D
A ground radial system can be constructed easily from field tele-
phone wire (WDl/TT) and can be kept with the radio. Cut the field
wire into twenty 45-foot lengths, and remove 6 inches of insulation
from one end. Using twine or a clamp, bundle together the uninsu-
lated (bare) ends. Attach a 2-foot length of thick wire to the bare
ends so that the thick wire extends about one foot beyond the wire
bundle. Solder the wire bundle to ensure good...

Antenna Handbook ____________________________ 
4-13
is a vertical wire, metallic pole, or another whip that is insulated
from the ground. It is placed so that the reflector, the whip, and the
distant station are on a straight line. The reflector will reflect radio
energy striking it and cause the energy to travel toward the distant
station, increasing the total energy radiated in the desired direction.
To work properly, the reflector must be longer than the whip. If the
reflector is shorter, it will act...

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MCRP 6-22D
The length of a vertical whip antenna is calculated from the follow-
ing formula:
For WD-l/TT
Half-Wave Dipole
The horizontal half-wave dipole (doublet) antenna  is used on short-
and medium-length sky wave paths (up to approximately 1,200
miles). Since it is relatively easy to design and construct, the dou-
blet is the most commonly used field expedient wire antenna. It is a
very versatile antenna; by adjusting the antenna’s height above
ground, the...