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Propagation describes how radio signals radiate outward from a transmitting source. A radio transmitter’s antenna emits radio waves much like the wave motion formed by dropping a stone in a pool of water.

This action is simple to imagine for radio waves that travel in a straight line in free space. The true path radio waves take, and how the earth’s atmosphere affects these waves, is more complex.

2. Earth’s Atmosphere The earth’s atmosphere is divided into three separate regions. The layers are the troposphere, the stratosphere, and the ionosphere. Most of the earth’s weather takes place in the troposphere, which extends from the earth’s surface to about 10 miles up. The weather variations in temperature, density, and pressure have a great effect on the propagation of radio waves. The stratosphere, which extends from roughly 10 to 30 miles up, has little effect on radio wave propagation.

The ionosphere, which extends from 30 to approximately 375 miles up, contains up to four cloud-like layers of electrically charged ions. It is this region and its ionized layers that enable radio waves to be propagated great distances. The ionosphere, and how it effects radio wave propagation, is discussed on page I-2. 3. Types of Propagation There are two basic modes of propagation: ground waves and sky waves.

Ground waves travel along the surface of the earth and are used primarily for short-range communications. Sky waves, reflected by the ionosphere, are “bounced” or reflected back to earth and provide a long-haul communications path, as well as short-range (0 to 180 miles or 300 kilometers [km]) communication in mountainous terrain.

a. Ground Waves. Ground waves consist of three components: surface waves, direct waves, and ground-reflected waves.

(1) Surface Waves. Surface waves travel along the surface of the earth, reaching beyond the horizon. Eventually, surface wave energy is absorbed by the earth. The effective range of surface waves is largely determined by the frequency and conductivity of the surface over which the waves travel.

Bodies of water and flat land have the least amount of absorption, while desert and jungle areas have the greatest. For a given complement of equipment, the range may extend from 200 to 250 miles over a conductive, all-sea-water path.


Automatic Link Establishment Overview Automatic link establishment (ALE) is a communication system that permits HF radio stations to call and link on the best HF channel automatically without operator assistance.

Typically, ALE systems make use of recently measured radio channel characteristics stored in a memory matrix to select the best frequency. The system works much like a telephone in that each radio in a network is assigned an address (similar to a call sign). When not in use, each radio receiver constantly scans through its assigned frequencies, listening for calls addressed to it.

1. ALE Linking Sequence a. To reach a specific station, the radio operator simply enters an address, just like dialing a telephone number. The radio consults its memory matrix and selects the best available assigned frequency. It then sends out a brief digital message containing the identification (ID) of the destination.

When the receiving station hears its address, it stops scanning and stays on that frequency. The two stations automatically conduct a “handshake” to confirm that a link is established, and they are ready to communicate (see figure II-I). Figure II-1.

ALE Linking Sequence b. The receiving station, which has been squelched, will emit an audible alert and/or a visual indication of the ALE address of the station that called to alert the operator of an incoming call. At the conclusion of the call, either operator can “hang-up” or terminate the link;

a disconnect signal is sent to the other station and they each return to the scanning mode. The HF High Frequency in HF communications involve both LQA radios and multi-service channel radios.

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Counterproliferation Operations

The US military response to the threat, and actual use of NBC weapons is
counterproliferation. Counterproliferation is a multitiered, integrated approach intended to
deter NBC use and enable US forces to survive, fight, and win in an NBC environment.
Counterproliferation is built on four core capabilities: counterforce, active defense, passive
defense, and consequence management;

it is also enhanced by military support to
nonproliferation efforts. It includes the activities of the Department of Defense (DOD)
across the full range of US government (USG) efforts to combat proliferation (see Figure I-
1). Commanders at all levels are responsible for the integration and synchronization of
these four core capabilities into their overall operations in support of national
nonproliferation and counterproliferation objectives.

a. Counterproliferation exists across a sequence of mutually supporting operations
that form a continuum of interrelated activities that employ both offensive and defensive
measures. The success of efforts in one area impacts other functions throughout the
operational cycle. The focus of this publication is passive defense.

An awareness of how
passive defense fits within the counterproliferation operations concept is important because
passive defense operations can be impacted by the other three core capabilities.


Maintaining Preparedness

Maintaining military preparedness for potential operations in NBC environments
presents significant challenges and places extraordinary demands on commanders at all
echelons for a clear understanding of potential threats and the requirements for unity of
effort among US forces (service, interagency, joint, multiservice, and multinational) in the
US and abroad.

Threat assessment includes overseas areas of potential conflict as well as
US territory, with particular attention to the civilian infrastructure, military forces, types
of hazards that may be encountered (i.e., low-level exposure hazards), and facilities needed
to support the range of military operations.

Preparedness includes visibly and successfully
exercising service, joint, multinational, and interagency plans that demonstrate the
capability to operate in NBC environments because the use of NBC weapons could impact
strategic, operational, or tactical operations.

a. Background. Maintaining preparedness may include combat operations and
MOOTW such as peace operations, foreign humanitarian assistance, and other military
support to civil authorities (MSCA). This environment presents numerous opportunities for
US military operations to encounter antagonists possessing NBC weapons or toxic

b. Low-Level Exposure. In addition to the employment of NBC weapons by a threat,
maintaining preparedness includes being alert to other dangerous hazards that can persist
in the AO. Prevalent among those hazards are low-level radiation (LLR), depleted uranium
(DU), TIM, and biological agents (covertly or accidentally dispersed).

An LLR threat can
exist in certain expended munitions, damaged or destroyed equipment, or contaminated
shrapnel—as well as inadequate nuclear waste disposal, deterioration of nuclear power
facilities, or damage to facilities that routinely use radioactive material. LLR produces longterm
radiation exposure health consequences for personnel. DU found in munitions does
not present significant hazards as long as the round is intact.

However, care must be taken around vehicles that have been hit by DU rounds or fires where DU munitions are involved because inhalation and ingestion of DU dust and residue present a health hazard. TIM are often present in enormous quantities in the AO and can be released from industrial plants, transport containers, or storage facilities through battle damage or used as a desperation
measure during military operations.

The multiservice CBRN and other FM and MCWP of the army and NBC technique are contained, for
download and SS in FM 4, FM 7, FM 100 and c-1 protection doctrines.

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Field Manuals: US Army FM 21-31 – Topographic Symbols

Field Manuals: US Army FM 21-31 – Topographic Symbols

23.1. Joint Operations Graphics

a. Purpose and Scope. Joint Operations Graphics are produced in both ground and air versions. The ground version is designated as Series 1501; the air version is designated as Series 1501 AIR. Both versions are designed to provide common base graphics for use in combined operations by the ground and air forces of allied nations. The topographic information is identical on both the ground and air versions.

b. Unit of Vertical Measure. On the ground version, elevation and contour values are shown in meters. These values are converted to foot units on the air version.

c. Aeronautical Information. Both versions contain identical information regarding aerodromes and obstructions to pilotage. The air version contains additional information concerning aids to air navigation.

d. Shaded Relief. Both versions contain an identical representation of shading, to provide a rapid recognition of slope and landforms. The shading also serves as a means of correlating contours and elevations, with emphasis on the more significant terrain features.

e. Elevation Tints. Both versions contain a representative system of color tints which depict areas of the same elevation range. A key box on each version indicates the elevation ranges and their corresponding color tints. j. Symbols. The following approved symbols for Joint Operations Graphics are in addition to, or different from, the standard medium-scale symbols shown in figures 1 through 242

Survival-SHTF-Guide: US Army FM 21-31 – Topographic Symbols


This manual describes the topographic symbols and abbreviations authorized for use by all echelons in the interpretation of military maps, overlays, and related features and activities. 2. Scope This manual is divided into four chapters. a.

Chapter 1 contains general information on the use of topographic symbols, gives the basic scales for topographic maps, defines topographic maps, and discusses map detail, map accuracy, and map colors. b.

Chapter 2 gives examples and illustrations of topographic symbols arranged by categories, such as d r a i n a g e features, relief features, and roads. c. Chapter 3 gives topographic abbreviations, their scope and application. d.

Chapter 4 discusses marginal information. 3. References Appendix I is a list of publications which give detailed information on maps and mapping, foreign conventional signs and symbols, reference data for the various services, transportation and signal facilities, and abbreviations for administrative and electrically transmitted messages.

4. Symbols and Abbreviations a. Some of the symbols appearing on published maps may not agree entirely with those shown in this manual, since it is necessary to devise or modify symbols to portray conditions or features which are unique to the area being mapped. Consequently, before any map is used, the symbol legend appearing in the margin should be carefully studied.

The contours of a map and topo map from the USGS or other, shape, roads and features, lakes, vegetation, elevation gains, scale, railroad boundaries and other map symbology is all included in this download.

Us Army Field Manuals, tactics techniques and procedures, field manual should be excellent resource for your SHTF collection! These military field manuals or guides, US army manuals or military manuals are all FREE download manuals.

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