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

							Antenna Handbook ____________________________ 
4-25
and is used for a very narrow range of frequencies. By using the
antenna couplers that are part of many radio sets, the dimensions of
the inverted L can be modified to allow ground wave and short-
range sky wave propagation over a range of frequencies. Using a
vertical height of 35 to 40 feet, the following horizontal lengths will
give reasonable performance for short-range sky wave circuits.  
Table 4-5. Gain Versus Length.
Frequency Range (MHz)2.5 to 4.03.5 to 6.05.0 to 7.0
Horizontal Length (Feet)15010080Figure 4-18. Inverted L Antenna.INSULATORSANTENNA WIRERADIO
GROUNDl_
4l_
2 
						

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MCRP 6-22D
Orient the antenna like a dipole (i.e., the broad side of the antenna
should be toward the distant station). These lengths should not be
used outside the frequency ranges specified because the antenna
radiation pattern changes, and for frequencies much removed from
the range, the antenna will become directional off the wire end. (See
the sloping wire paragraphs on page 4-34 for using this directional
characteristic.) The inverted L antenna can be used as a substitute
for the dipole; however, it has less gain than a dipole, and its radia-
tion pattern varies with frequency (unlike a dipole). Figures 4-19,Figure 4-19. 40-Foot Inverted L (Vertical Pattern),
150 Feet Long.TAKE-OFF ANGLE3 MHz10°10°20°20°30°30°40°40°50°50°60°60°70°70°80°80°90°151050-5-10-51015dBi 
						

							Antenna Handbook ____________________________ 
4-27
4-20, and 4-21 on page 4-28 illustrate vertical patterns of various
inverted L antennas. Characteristics are—
Frequency range:Less than 2:1 over design frequency
Polarization:Vertical from vertical section
Horizontal from horizontal section
Power capability:1,000 watts
Radiation pattern
Azimuthal (bearing):Omnidirectional
Vertical (take-off angle):See figures 4-19, 4-20, and 4-21 on
page 4-28 Figure 4-20. 40-Foot Inverted L Antenna (Vertical Pattern),
80 Feet Long.TAKE-OFF ANGLE5 MHz10°10°20°20°30°30°40°40°50°50°60°60°70°70°80°80°90°151050-5-10-51015dBi 
						

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MCRP 6-22D
Figure 4-21. 40-Foot Inverted L (Vertical Pattern),
100 Feet Long.
Sloping Vee
The sloping vee is a medium- to long-range sky wave antenna that
is simple to construct in the field. Antenna gain and directivity
depend on the leg length. For reasonable performance, the antennaTAKE-OFF ANGLE4 MHz10°10°20°20°30°30°40°40°50°50°60°60°70°70°80°80°90°151050-5-10-51015dBi 
						

							Antenna Handbook ____________________________ 
4-29
should be at least one wavelength long, but preferably several
wavelengths long (see fig. 4-22).
Figure 4-22.  Sloping Vee Antenna.INSULATORSANTENNA WIRELEAD WIRE
RADIO
GROUNDPOLE
POLE 
						

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MCRP 6-22D
A compromise tactical sloping vee can be constructed using 500-
foot legs and a 40-foot support mast. The angle between the two
legs is adjusted to provide maximum radiation at the desired take-
off angle. Table 4-6 shows the angles between legs (apex angle) that
will give poor results for the distances indicated.
To make the antenna directional, use terminating resistors on each
leg on the open part of the vee. The terminating resistors should be
300 ohms and be capable of handling one-half of the transmitter’s
power output. These terminations are either procured or fabricated
locally using supply system parts (100-watt, 106-ohm resistor).
Using the terminating resistors, the antenna is aimed so that the line
cutting the vee in half is pointed at the distant station.Table 4-6. Angle Between Antenna Legs
for Poor Results.
Path Length
 (Miles)
700 to 10001000 to 1500over 1500
Apex Angle
(Degrees)
604530 
						

							Antenna Handbook ____________________________ 
4-31
The sloping vee is normally fed with a 600-ohm, open-wire feed
line. One side of the feed line is connected to one leg with the other
side connected to the other leg. The open-wire feed line can be con-
nected to a 12 to 1 balun, which is then connected to standard coax-
ial cable. Figures 4-23, 4-24 on page 4-32, and 4-25 on page 4-33
illustrate the vertical patterns for various sloping vee antennas.Figure 4-23. 40-Foot Sloping Vee (Vertical Pattern),
500 Feet Long, 30° Apex  Angle.TAKE-OFF ANGLE9 MHz10°10°20°20°30°30°40°40°50°50°60°60°70°70°80°80°90°151050-5-10-51015dBi 
						

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MCRP 6-22D
Characteristics are—
Frequency range:3 to 30 MHz
Polarization:Horizontal
Power capability:Depends on terminating resistors
Radiation pattern
Azimuthal (bearing):Directional (20° either side of
direction of radiation)
Vertical (takeoff angle):See Figures 4-23, 4-24 on page
4-32, and 4-25 on page 4-33 Figure 4-24. 40-Foot Sloping Vee Antenna (Vertical Pattern),
500 Feet Long, 45° Apex Angle.TAKE-OFF ANGLE10°10°20°
20° 30°30° 40°40° 50°50° 60°60° 70°70° 80°80° 90°151050-5-10-51015dBi  3 MHz9 MHz 
						

							Antenna Handbook ____________________________ 
4-33
Sloping Wire
The sloping wire antenna is simple and easy to construct. It requires
only one support (see fig. 4-26 on page 4-34). A version of the long
wire antenna, the sloping wire produces best results when it is long
compared to a wavelength. Tactical sloping wires vary in length
from 45 to over 500 feet. The shorter lengths perform rather poorly
and should be used only when no other antenna can be erected. TheTAKE-OFF ANGLE10°10°20°
20° 30°30° 40°40° 50°50° 60°60° 70°70° 80°80° 90°151050-5-10-51015dBi  3 MHz9 MHzFigure 4-25. 40-Foot Sloping Vee Antenna (Vertical Pattern),
500 Feet Long, 60° Apex Angle. 
						

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MCRP 6-22D
longer lengths (e.g., 250 feet, 500 feet) can produce good radiation
for medium to long sky wave paths.
A sloping wire can be either terminated or unterminated. If avail-
able, use 600-ohm termination because this makes the antenna
impedance fairly constant, and a balun can be used to match the
antenna to a transmitter. If the antenna is unterminated, use a cou-
pler to match the transmitter to the antenna.
The low end of the wire should be oriened toward the receiving sta-
tion. If the wire is unterminated, feed the antenna at the low end. If
a terminating resistor is used, feed the antenna low end. Figure 4-27
and figures 4-28 and 4-29 on page 4-36 illustrate the vertical pat-
terns for various sloping wire antennas.INSULATORANTENNA WIREGROUNDRADIOMAXIMUM RADIATIONFigure 4-26.  Sloping Wire.