Module 10—Introduction to Wave Propagation, Transmission Lines, and Antennas
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Now that you have completed this chapter, let’s review some of the new terms, concepts, and ideas you
have learned. You should have a thorough understanding of these principles before moving on to chapter 2.
WAVE PROPAGATION is an invisible force that enables man to communicate over long distances. Wave
transmission can take many forms, such as LIGHT, SOUND, and RADIO.
LIGHT is a form of wave motion that can be seen. Heat cannot normally be seen, but can be felt.
Radio waves cannot be seen or felt.
WAVE MOTION can be seen in action by throwing a
pebble into a pool of still water. The ripples that move toward the edge of the pool demonstrate the
The TRANSVERSE WAVE is a type of wave motion. Radio, light, and heat waves are examples
of transverse waves.
The LONGITUDINAL WAVE is another type of wave motion. The sound wave is the only
example of a longitudinal wave given in this text.
SOURCE, MEDIUM, AND DETECTOR
are the three requirements for all wave motion.
A SOURCE can be anything that emits or expends energy (waves).
MEDIUM is the vehicle for carrying waves from one point to another. Water, air, metal, empty
space, etc., are examples of a medium. Empty space is considered a medium for electro-magnetic waves but not a
medium for sound waves.
The SOUND DETECTOR absorbs the waves emitted by the source. The
human ear is an example of a detector.
HERTZ, which is abbreviated Hz, is used in lieu of
"cycle per second" when referring to radio frequencies.
VELOCITY OF PROPAGATION is the
speed (or rate) at which the crest of a wave moves through a medium. Velocity can be calculated by using the
V = λ f
Where v is velocity of propagation and is expressed in feet (meters) per second,
λ is the wavelength in feet (meters), and f is the frequency in hertz.
REFLECTION occurs when a wave strikes an object and bounces back (toward the source). The wave
that moves from the source to the object is called the INCIDENT WAVE, and the wave that moves
away from the object is called the REFLECTED WAVE.
The LAW OF REFLECTION states:
The angle of incidence is
equal to the angle of reflection.
REFRACTION occurs when a wave traveling through
two different mediums passes through the BOUNDARY of the mediums and bends toward or away from
DIFFRACTION can account for the ability of the AM radio waves (due to their low
frequency) to travel over a mountain, while FM and TV signals (due to their higher frequencies) are blocked.
The DOPPLER EFFECT is the apparent change in frequency of a source as it moves toward
or away from a detector. It can affect the operation of equipment used to detect and measure wave energy.
SOUND can be audible to the human ear or it can be outside the hearing range.
NOISE AND TONES are the two general groups that broadly classify ALL sounds.
PITCH, INTENSITY, AND QUALITY are the three basic characteristics of sound. Pitch
describes the frequency of sound. Intensity describes how much
energy is transmitted. Quality enables us to distinguish one sound from
The DENSITY of a MEDIUM, TEMPERATURE, and ATMOSPHERIC
affect the velocity of sound. If temperature, density, or pressure increases, the velocity of sound increases and
ACOUSTICS is the science of sound and relates to the sense of hearing.
ECHO is an example of reflection. Sound echoes are used in sonar and depth finders to determine
or measure the range of an object or the depth of the ocean bottom.
REVERBERATION is the
multiple reflections of sound waves. The prolonged roar of thunder is caused by reverberations. With underwater
sound equipment, reverberations of nearby objects may interfere with returning echoes from actual targets.
INTERFERENCE occurs when two waves move simultaneously through a medium. They can interfere
constructively, destructively, or produce a resultant of zero.
RESONANCE occurs when an
objects vibrates (or resonates) at its natural frequency. When different frequencies are produced inside a cavity,
the sound from the cavity sounds louder at its resonant frequency than at all other frequencies.
is any disturbance that distracts from or distorts the quality of sound.
A PHOTON is the
smallest unit of radiant energy that makes up light waves and radio waves.
(Å) units are used for measuring the wavelength of light. One angstrom = 1055-10
The VISIBLE SPECTRUM contains all the colors between infrared and ultraviolet.
INFRA-RED and ULTRA-VIOLET are invisible to the human eye.
PRIMARY COLORS of light are red, green, and blue. These primaries can be mixed to make any color
between red and violet. If the three colors are mixed equally, they produce white light.
The COMPLEMENTARY COLORS of light are magenta, yellow, and cyan. They are produced by
mixing any two of the primary colors together in overlapping beams.
The SPEED OF LIGHT
in empty space is considered to be 186,000 miles per second (or 300,000,000 meters per second). This speed varies
in different mediums, but the constant of 186,000 miles per second is always used as the speed of light.
The ELECTROMAGNETIC SPECTRUM is the complete range of electromagnetic frequencies from 3 kHz to
beyond 300,000 THz. Audio frequencies (15 Hz-20 kHz) are not electromagnetic energy and are not included in the
The ELECTROMAGNETIC FIELD consists of an ELECTRIC FIELD and a
MAGNETIC FIELD. These fields are responsible for the transmission and reception of electromagnetic energy
through free space.
ANSWERS TO QUESTIONS Q1. THROUGH Q48.
A1. Propagation means spreading out.
A2. A wave is a disturbance which moves through a
A3. A means of transferring energy from one place to another.
A4. Sound waves, light waves, radio waves, heat waves, water waves.
A5. Transverse waves.
A6. Radio waves, light waves, and heat waves.
A7. A sound wave.
A8. A source, medium, and detector (receiver).
sequence of events, such as the positive and negative alternation of electrical current.
A10. The space
occupied by one cycle of a radio wave at any given instant.
A11. The law of reflection states: The angle
of incidence is equal to the angle of reflection.
A12. When the incident wave is nearly parallel with
A13. When the incident wave is perpendicular to the surface. Also a dull (or black) surface reflects very little
regardless of the angle.
A14. The density of the two mediums, and the velocity of the waves.
A15. The Doppler effect.
A17. No. The average human ear cannot hear all sounds
in the infrasonic and ultrasonic regions.
A18. An amplifier.
A19. A source, medium, and
A20. Noise and tones.
A21. Pitch, intensity, and quality.
20 Hz to 20 kHz.
A23. The amount of energy transmitted from a source.
A25. Velocity increases as density decreases and temperature increases.
A31. Mechanical, electrical, and chemical.
A33. Angstrom unit.
A34. Red, green and blue.
Introduction to Matter, Energy, and Direct Current,
to Alternating Current and Transformers, Introduction to Circuit Protection,
Control, and Measurement
, Introduction to Electrical Conductors, Wiring Techniques,
and Schematic Reading
, Introduction to Generators and Motors
Introduction to Electronic Emission, Tubes, and Power Supplies,
Introduction to Solid-State Devices and Power Supplies
Introduction to Amplifiers, Introduction to
Wave-Generation and Wave-Shaping Circuits
, Introduction to Wave Propagation, Transmission
Lines, and Antennas
, Microwave Principles,
, Introduction to Number Systems and Logic Circuits, Introduction
to Microelectronics, Principles of Synchros, Servos, and Gyros
Introduction to Test Equipment
, Radar Principles,
The Technician's Handbook,
Master Glossary, Test Methods and Practices,
Introduction to Digital Computers,
Magnetic Recording, Introduction to Fiber Optics