Reconnaissance and Surveillance Leaders Course RECONNAISSANCE & SURVEILLANCE LEADERS COURSE RECONNAISSANCE AND SURVEILLANCE COMMUNICATIONS

Reconnaissance and Surveillance Leaders Course

RECONNAISSANCE & SURVEILLANCE LEADERS COURSE

RECONNAISSANCE & SURVEILLANCE LEADERS COURSE

RECONNAISSANCE AND SURVEILLANCE COMMUNICATIONS

RECONNAISSANCE AND SURVEILLANCE COMMUNICATIONS


RECONNAISSANCE AND SURVEILLANCE

COURSE

HF COMMUNICATIONS

RADIO WAVE PROPAGATION


THE CHALLENGES FACING YOU, THE HF RADIO OPERATOR, ARE TREMENDOUS!

Radio Wave Propagation

AS SELECTED LEADERS YOU MUST:

• POSSES MORE THAN A WORKING KNOWLEDGE OF YOUR EQUIPMENT

• BE ABLE TO ANSWER YOUR SUBORDINATES QUESTIONS


TERMINAL LERNING OBJECTIVE

Action: Implement the principles of Radio Wave Propagation

Condition: Denied the use of references

Standard: Answer test questions correctly that pertain to Radio Wave Propagation


Administrative

Safety: In an emergency, please exit through the exit doors and get a headcount outside in the parking lot

RiskAssessment: Low

Environmental

Considerations: If you brought it in, take it with you!

Note: Do not be afraid to ask questions or participate in discussion, just raise your

hand before speaking.


Evaluation

• You will be evaluated on this subject on Wednesday and during the STX/FTX

• You will be given a 50 question test

• You must correctly answer 35 out of 50 to receive a go


ENABLING LERNING OBJECTIVE #1

Action: Identify principles of Ground Wave Propagation


Standard: To receive a go, the student must take a 50 question multiple choice test and answer 35 questions correctly



• To understand Radio Wave Propagation, you must first understand what propagation is and some of the basic properties that affect propagation.

• Many of these properties are common everyday occurrences that you may already be familiar with



AS YOU WILL LEARN BY STUDYING THIS

SUBJECT,RADIO WAVES PROPAGATE OR SPREAD

OUT



Q: WHAT WERE SOME EARLY METHODS TO EXTEND COMMUNICATIONS RANGE?

•HAND AND ARM GESTURES

•BEATING ON A HOLLOW LOG

•SMOKE SIGNALS

•COURIER AND POSTAL SYSTEM

•STILL NEEDED TO EXTEND RANGE AND SPEED



DURING THE LATTER PART OF THE 19th CENTURY BOTH SPEED AND DISTANCE WERE GREATLY OVERCOME WITH:

•THE INVENTION OF THE TELEGRAPH

• THE INVENTION OF THE RADIO TRANSMITTER



• HEINRICH HERTZ Discovered how to send a message in the form of a radio wave:

•This is where the term “Hertz” comes from

•One Hertz is one cycle per second:



• A radio wave that has a frequency of 2 KHZ cycles at 2000 times a second

• 2 MHZ cycles at 2,000,000 times a second



VLFLFMFHF

VHF

UHF

SHF

EHF

COSMICGAMMA

3000 Hz (3 KHz)

30,000 Hz (30 KHz)

300,000 Hz (300 KHz)

3,000,000 Hz (3 MHz)

30 MHz

300 MHz

3 GHz

30 GHz

300 GHz

3 THz

300,000 THz

MILITARY COMMUNICATIONS

RADARMICROWAVES

INFRA-RED

VISIBLE LIGHTULTRA-VIOLET LIGHT

X-RAY

T = TERAG = GIGAM = MEGAK = KILO



• A well designed, properly maintained LOS radio system will operated day after day, year after year with little or no significant outages

• Even if an HF radio system is well designed, the operator must continually adjust the system to compensate for changing terrestrial environment

However…….



• High Frequency (HF)radio waves travel by two primary means:


Ground Wave Propagation

• Ground waves are affected by three factors:

1. Electrical characteristics of the earth

-Ground is negative

-Path of least resistance

2. Power output & frequency of the transmitter

- More power and higher frequency= further ground wave distance

3. Shape and conductivity of the earth

-Obstacles in transmission path?



•Obstacles include:

• Mountains

•Cliffs

•Vegetation

•Man-Made Objects



•There are three components to a ground wave:

Direct Wave

Ground Reflected Wave

Surface Wave



Direct Wave

• Travels directly from transmit to the receive antenna

• Limited by LOS distance

•Distance can be extended by raising the transmit or receive antenna



Ground Reflected Wave

• Reaches the receiving antenna after being reflected by the surface of the earth



Surface Wave

• Follows the curvature of the earth until it is too weak to be received or encounters an obstacle




Ground Wave Review

Q: What are the three components to a ground wave?A: Direct Wave, Ground Reflected Wave and Surface Wave

Q: What obstacles can impede the path of a ground wave?A: Mountains, power lines, steep cliffs, heavy vegetation and man-made objects

Q: What other factors influence how far a ground wave will propagate?

A: Transmitter power and frequency (Hertz)




Q: We know that an HF radio wave will travel on or near the ground, what other way can an HF radio wave propagate?

A: Through the atmosphere, called a “Sky Wave”


Sky Wave Propagation


ENABLING LERNING OBJECTIVE #2

Action: Identify principles of Sky Wave Propagation


Standard: To receive a go, the student must take a 50 question multiple choice test and answer 35 questions correctly



• Sky wave propagation uses the earth’s atmosphere as it’s medium

• You must be familiar with the different parts of the atmosphere and how it effects the propagation of radio waves

• Long Range Surveillance teams rely heavily on sky wave propagation to communicate intelligence and complete their mission




• High Frequency (HF) communications rely on portions of the atmosphere for long range communications

• The atmosphere varies with altitude, geographic locations, time of day and season

• There are three layers of the atmosphere, which will be discussed later in detail

Q: How far do you think you can communicate using sky wave propagation?

A: Unlimited


Sky Wave PropagationIONIZATION

• AN ATOM IS NEUTRALITY CHARGED

• IONIZATION OCCURS WHEN:

THE SUN’S ULTRAVIOLET LIGHT WAVES STRIKE A GAS ATOM, AND LITERALLY KNOCK AN

ELECTRON FREE FROM ITS PARENT ATOM CREATING A LAYER OF OPPOSITELY CHARGED PARTICLES

• THIS LAYER ALLOWS HF RADIO WAVES TO BE REFRACTED BACK TO EARTH


IONIZATION


Sky Wave PropagationIONIZATION

• There are certain locations, seasons and times of day when there is more of the sun striking the atmosphere.

Q: What season do you think ionizations occurs at a greater level?

A: Summer



RECOMBINATION

• SINCE IONIZATION ONLY HAPPEN DURING DAYLIGHT, A REVERSE PROCESS CALLED RECOMBINATION OCCURS AT NIGHT.

• EVENTUALLY, DO TO THE ABSENCE OF UV RAYS ,ELECTRONS WILL MERGE WITH THE PARENT ATOMS CAUSING A NEUTRAL STATE



Q: What are the three layers of the atmosphere?

Troposphere

Stratosphere

Ionosphere



TROPOSPHERE

• 4 TO 11 MILES ABOVE THE EARTH

• ALL WEATHER TAKES PLACE

• CLOUDS FORM

• TURBULENCE

• TEMPERATURE VARIES

HAS A GREAT EFFECT ON THE PROPAGATION OF RADIO WAVES



STRATOSPHERE

• BETWEEN TROPOSPHERE AND IONOSPHERE

• CONSTANT TEMPERATURE

• LITTLE WATER VAPOR

HAS RELATIVELY NO EFFECT ON RADIO WAVES



IONOSPHERE

• 30 - 250 MILES ABOVE THE EARTH

• FOUR CLOUD-LIKE LAYERS

• USED FOR LONG DISTANCE COMMUNICATIONS

MOST IMPORTANT REGION OF THE ATMOSPHERE



Q: We know that the Ionosphere is composed of 4 cloud like layers. Can anybody name some of these layers?

• Four distinct layers during the day-

• One layer at night- F

D E F1 F2



D REGION

• EXISTS ONLY DURING DAYLIGHT HOURS

• IONIZATION IS LOW BECAUSE THE E & F LAYERS HAVE ALREADY ABSORBED MOST OF THE UV RAYS

• HIGH FREQUENCIES PASS RIGHT THROUGH IT

D LAYER HAS LITTLE EFFECT ON HF RADIO WAVES



E REGION

• EXISTS ONLY DURING DAY LIGHT HOURS

• USED FOR HF RADIO TRANSMISSIONS LESS THAN 1500 MILES

• KNOWN AS THE KENNELLY-HEAVISIDE LAYER

• CAN REFRACT FREQUENCIES UP TO 20 MHZ


Sky Wave PropagationF REGION

• IONIZED ALL OF THE TIME

• TWO LAYERS DURING THE DAY (F1 AND F2)

• ONE LAYER AT NIGHT (F)

• RESPONSIBLE FOR HF LONG RANGE COMMUNICATIONS GREATER THAN 1500 MILES

• EXTREMELY USEFUL LAYER FOR HF COMMUNICATIONS







Variations in the Ionosphere

• Regular: Variations that scientists can predict because they happen at regular intervals:

• Seasonal Variations -Summer/Winter

• 11 year Sunspot Cycle –An 11 year cycle in which sunspot activity increases or decreases. Sunspots increase ionization.

• 27 Day Sunspot Cycle –It takes the sun 27 days to rotate on its axis, increasing and decreasing ionization


Sky Wave PropagationVariations in the Ionosphere

Irregular Variation: These are the variations that cannot be predicted, but are known to occur:

• Sporadic E- Irregular cloud like patches of unusually high ionization, often in the E region. Cause is unknown, and varies significantly with latitude.

• Sudden Ionosphere Disturbance (SID) –Occur without warning and may last several hours. Long distance HF propagation is totally blanked out.

• Ionospheric Storms –Caused by disturbances in the Earth’s magnetic field. Are tied solar eruptions and occur 18 hours after a SID.



SKY WAVE PROPAGATION:

• DEPENDS UPON THE IONOSPHERE TO PROVIDETHE SIGNAL PATH BETWEEN THE TRANSMIT ANTENNA AND THE RECEIVE ANTENNA

• THE IONOSPHERE BENDS THE RADIO WAVE BACK TO EARTH, THIS BENDING IS CALLED REFRACTION




THE AMOUNT OF REFRACTION DEPENDS ON THREE MAIN FACTORS:

1. THE DENSITY OF IONIZATION IN A PARTICULAR REGION

2. THE FREQUENCY OF THE RADIO WAVE

3. THE ANGLE AT WHICH THE WAVES ENTER THE REGION



Station A Station B

MAXIMUM ELECTRON DENSITY

SignalAngle of Incidence



Q: What do you think the area between Station A and Station B is called

A: Skip Distance



Skip Zone is the area of silence between the point where the ground wave becomes too week and the sky wave returns to earth





ABSORPTION IN THE IONOSPHERE

• PROVIDES THE GREATEST ADVERSE EFFECT ONRADIO WAVES

• EFFECTS BOTH THE STRENGTH OF RECEIVED SIGNALS AND THE ABILITY TO COMMUNICATE OVER LONG DISTANCES



REFERENCES:

o Student Handout

o FM 11-65

o FM 11-64

o FM 24-18


Review/Summary

• The Terminal Learning Objective is to identify the principles of Radio Wave Propagation (RWP). When tested you will be denied the use of references and must answer 35 out of 50 questions correctly.


QUESTIONS?


Review/Summary

1. What are the three parts of a ground wave?

Direct Wave, Ground Reflected Wave, Surface wave

2. What is refraction?

Ionosphere bending a radio wave back to earth

3. What are the three irregular ionospheric variations?

Sporadic E, Sudden Ionospheric Disturbance (SID) and Ionospheric Storms


Review/Summary

We have just covered principles of Radio Wave Propagation. Our next lesson will cover Antenna Theory

Documents

Reconnaissance and Surveillance Leaders Course RECONNAISSANCE & SURVEILLANCE LEADERS COURSE RECONNAISSANCE AND SURVEILLANCE COMMUNICATIONS