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TABLE 2-2. AMPLIFIER/COUPLER CONTROLS AND INDICATORS
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TM-11-5820-919-12 Radio Set AN/PRC-104(A) (NSN
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Figure 2-2. Antennas for Use With the Radio Set


TM 11-5820-919-12
SECTION II
OPERATING CONSIDERATIONS
2-16.
GENERAL.
2-23.
If the tactical situation permits, a simple half-
wave dipole or the Near Vertical Incidence Skywave
(NVIS) twin dipole antenna can be used between 2 and
2-17.
This section provides information to assist the
12 to extend the range of the radio considerably )by
operator in selecting the proper antenna, frequency,
utilizing the "skip" phenomenon.  In this mold the radio
mode, and site for achieving best communication with
waves are bounced off the ionosphere and back to the
this radio set.  Refer to Appendix II for, information on
earth's surface providing coverage to 300 miles or more.
propagation of radio waves and some situational
The twin dipole may' )be used at frequencies above 12
examples for optimizing radio comication.
NMHz, but automatic tuning may not work at all
2-18.
OPTIMIZING COMIMUNICATION WITH THE
frequencies.  The nature of the dipole or NV'IS antenna
AN/PRC-104.
optimizes the skip effect but final results depend  on
existing propagation characteristics.
2-19.
The readability and effectiveness of radio
communications in the high frequency (HF) range is
2-24.
When using an antenna that has directional
dependent on several factors..
characteristics, try to orient the antenna so it is most
sensitive in the direction toward the other station.  For
1. Type of antenna used
example, a dipole antenna is most effective in a direction
2. Operating frequency selected
perpendicular to the wire. The NVIS antenna is omri-
3. Terrain around transmitting site
directional (same sensitivity in all directions),  so
4. Time of day'
orientation of the antenna is not important.
5. Geographic location and distance between
stations
2-25.
A list of standard and alternate antennas that
6. Atmospheric conditions
can be used with the AN/PRC-104, with the major
7. The effects of the ionosphere on radio waves
characteristics of each, is shown below.
2-20.
The radio operator can control, to some
WHIP ANTENNA
Omnidirectional (360 degree
degree, only the first four or five of these factors.  The
radiation pattern)
others affect propagation characteristics and background
interference, and are beyond operator control.
The
Easily and quickly assembled and
antenna and frequency are the most important factors
erected
under operator control, and should be selected to best
suit the propagation characteristics and distance of the
Excellent portability
link.
Several frequencies will probably have been
Very poor gain; limited range (<10
assigned from upper echelon.
They will have been
mi) over land, even in hill terrain.
selected in various portions of the band in order to allow
Range may be better under good
a frequency change when propagation conditions
propagation conditions.
change.
NEAR VERTICAL
Omnidirectional
INCIDENCE
2-21.
ANTENNA SELECTION (Figure 2-2).
SKYWAVE (NVIS)
Requires fairly large clear area 60
feet square) for proper erection
2-22.
The field environment, tactical situation, and
range required determine the antenna selection.  If the
Good gain; extended range (0 to
radio set is to be used while on the move (manpack
300 miles)
operation), the whip antenna supplied with the antenna is
used. For most short range requirements using ground
HALF-WAVE
Bidirectional (perpendicular to
wave, the whip antenna will be satisfactory up to 10 miles
DIPOLE
wire)
over land.  However, over sea water, this antenna will
provide reliable communications up to 100 miles.
Good portability
2-5


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