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FM 11-23
APPENDIX B
TROPOSPHERIC SCATTER RADIO PLANNING FACTORS
B-1.
General
Section W. INTRODUCTION
a. Plans and operations personnel must be familiar
with the characteristics of tropo radio
equipment in addition to the characteristics of
other types of multichannel radio equipment.
OUTER SPACE
This familiarity will be helpful when selecting 400
the type of equipment to be used to provide the
//FLAY R / NOTE: F 1
AND F 2
multichannel communications required by the 250 LAYERS COMBINE AT
tactical situation. Only those basic features in- NIGHT TO FORM A
volving tropo radio propagation and factors to be
COMMON F LAYER.
considered in employment of tropo radio equip- a175
ment are discussed in the following paragraphs. E LAYER
More complete details relative to techniques of 90
multichannel radio communications are contained -2
in FM 24-21 and in appropriate radio engineer-
LAYER
ing publications and technical manuals. z 50
b. Tropo radio provides extremely reliable, STRATOSPHERE
high quality voice, teletypewriter, and data cir-
-_
cuits over extended distances. Because of its
TROPOSPHERE
method of radio wave propagation, tropo radio is O
not limited to line-of-sight sitings, normally a
FM 11-367-B-I
factor in microwave and VHF radio employment. Figure B-1. Average layer distribution of the atmosphere.
The capabilities (range, channel capacity, mobility,
etc) of tropo radio equipment vary according to some extent the ability to refract (bend) radio
to their design characteristics. To meet specific waves. The amount of refraction depends on such
requirements, tropo radio equipments are confi-
(turbulence,
factors as atmospheric conditions (turbulence,
gured into numerous types of vanized or shelter- temperature, atmospheric pressure, ionization of
mounted arrangements. The equipment organic to air molecules, etc), frequency of the transmitted
the light and heavy tropo companies is but one radio
radio
wave,
wave,
and
and
transmission
transmission
power.
power.
part of the overall family of tactical tropo radio
equipments.
B-3. Characteristics of Troposphere
a. Virtually all of the earth's weather pheno-
B-2. The Earth's Atmosphere mena occurs in the troposphere region of the ata.
The earth's atmosphere is separated into mosphere. Here, the constant motion of the air
several layers and each layer possesses properties causes turbulence, or eddies, to be formed. This
that determine the most effective method of radio turbulence is most intense near the earth' surface
wave propagation to be used for long distance and gradually diminishes with height. Normally,
communications. These
These layers are as follows: the as temperature the height and increases, barometric a steady pressure decrease occurs. in the
temperature and barometric pressure occurs. A
stratosphnd F lere and the laytropospher, he levels at combination of metrological variables, such as the
stratosphere, and the troposphere. The levels at amount of water vapor in the air, temperature,
which these layers occur are shown in figure B-1.
pressure, and air turbulences, determines the
b. Regardless of its height, each layer possesses refraction index of the troposphere.
B-1