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

Antenna Handbook ____________________________ 
2-25
Example: 3 half-wavelengths at 7 MHz is—
Length (meters) = 150 (N - 0.05)
Frequency in MHz
 = 150 (3 - .05)
7
 = 150 x 2.95
7
 = 442.50
7
 = 63.2 meters 

2-26 ____________________________________ 
MCRP 6-22D
Section IV. Antenna Orientation
The orientation of an antenna is extremely important. Determining
the position of an antenna in relation to the points of the compass
can make the difference between a marginal and good radio circuit.
AZIMUTH
If the azimuth of the radio’s path is not provided, determine it by the
best available means. The accuracy required depends on the radia-
tion pattern of the directional antenna. If the antenna beamwidth is
very...

Antenna Handbook ____________________________ 
2-27
10° is of little consequence. In transportable operation, the rhombic
and vee antennas may have such a narrow beam that great accuracy
is required to determine azimuth. The antenna should be erected for
the correct azimuth. Great accuracy is not required to erect broad-
beam antennas.
Unless a line of known azimuth is available at the site, the direction
of the path is best determined by a magnetic compass. Figure 2-12
on page 2-28 is a map of magnetic...

2-28 ____________________________________ 
MCRP 6-22D807060504030201001020304050607080
807060504030201001020304050607080
180
180
180
180
160
160
160
160
140
140
140
140
120
120
120
120
100
100
100
100
8080
8080
6060
6060
4040
4040
2020
2020
00
60E
60W
60W55W50W45W40W35W30W25W20W15W10W5W0E5E10E20E25E40E
55W45W50W40W35W30W25W20W
15W
10W
5W0
5E
50E40E35E30E25E20E15E10E10E15E20E25E30E35E40E50E60E
35E
5W
5W5E
10E15E20E
25E35E30E40E
50E60E
0
10W
30E
SMP
NMPFigure 2-12. Magnetic Declination Over the World. 

Antenna Handbook ____________________________ 
2-29
Transmission and Reception of Strong Signals
After an adequate site has been selected and the proper antenna ori-
entation obtained, the signal level at the receiver will be propor-
tional to the strength of the transmitted signal.   WARNINGEXCESSIVE SIGNAL STRENGTH MAY RESULT IN ENEMY IN-
TERCEPT AND INTERFERENCE OR IN YOUR INTERFERENCEWITH ADJACENT FREQUENCIES.
If a high-gain antenna is used, a stronger signal can be obtained.
Losses between the...

Chapter 3
Transmission Lines
Transmission lines (antenna feed lines) conduct or guide electrical
energy from the transmitter to the receiver. This chapter is oriented
primarily toward transmission lines with field expedient antennas.
For standard issue radios and antennas, use the issued coaxial cable.
As long as radios, cables, and antennas are maintained in working
order, they will operate as designed and won’t require any adjust-
ments or changes based on the information in this chapter.
PROPERTIES...

3-2 _____________________________________ 
MCRP 6-22D
are equal and opposite (i.e. at the moment one of the conductors
supports a positive voltage with respect to ground, the other sup-
ports a negative voltage of equal magnitude). Some balanced lines
carry a third conductor in the form of a braided shield, which acts as
ground. Conductor spacings up to several centimeters are com-
monly used. Figure 3-1 shows balanced and unbalanced lines.
Figure 3-1. Balanced and Unbalanced Transmission Lines.PLASTIC...

Antenna Handbook ______________________________ 
3-3
Unbalanced Line. The unbalanced line is usually open single-wire
line or coaxial cable. It is one-half of a balanced line.
Nonresonant Line. A nonresonant line is a line that has no stand-
ing waves of current and voltage. It is either infinitely long or is ter-
minated in its characteristic impedance. Because there are no
reflections, all of the energy passed along the line is absorbed by the
load (except for the small amount of energy dissipated by...

3-4 _____________________________________ 
MCRP 6-22D
A radio wave consists of electric and magnetic fields arranged per-
pendicularly to each other and to the direction the wave travels. The
impedance associated with this wave is the ratio of the potential dif-
ference (voltage) to the current (amperage) at a given point along a
transmission line. The following formula illustrates this.
In transmission lines, because of the length-frequency relationship,
the characteristic impedance is more often...

Antenna Handbook ______________________________ 
3-5
energy (lowest system loss) is achieved (i.e., the transmitter or
receiver, transmission line, and antenna are all the same imped-
ance), and the best possible transfer of signal energy will occur.
Optimizing Line Length
When it is necessary to use a transmission line whose impedance is
significantly different from that of the load, it is possible to make
good use of standing waves and the repetitive impedance variations
along the line to match the...