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46 Cards in this Set

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define this band of the electromagnetic spectrum and describe what signals are commonly used in it: extremely low frequency ELF
3-30Hz, long range signals, subs operating BEYOND NORMAL MISSION DEPTH. rarely used due to extremely large antenna required
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Super Low Frequency SLF
common power grids freqs (50-60 Hz) us and russian deep sea coms
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Ultra Low Frequency ULF
300Hz-3Khz commonly used for radio coms in mines, excellent earth-penetrating properties. also can be used for sub coms
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Very Low Frequency VLF
3 - 30Khz long range signals to subs operating at NORMAL MISSION SPEEDS AND DEPTHS. crucial comms during hostilities and used as backup to comms blacked out by nuclear activity
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Low Frequency LF
30Khz - 300Khz fleet multi-channel broadcast system.
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Medium Frequency MF
300Khz - 3Mhz primarily by navy for ground wave transmissions. commercial AM broadcasts, includes international distress freqs.
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: High Frequency HF
3-30 Mhz most commonly used for medium and long range terrestrial radio coms
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Very High Frequency VHF
30 300Mhz normally used for LOS of just beyond
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Ultra High Frequency UHF
300Mhz - 3 Ghz LOS comms, tatical voice transmissions
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Super High Frequency SHF
RADAR AND SATELLITE COMMS normally used for LOS or just beyond
define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Extremely High Frequency EHF
30 - 300Ghz radio astronomy, experimental stage
define and discuss: frequency
the number of cycles that occur in one second. usually expressed in hertz
define and discuss: wavelength
one 360 degree cycle. is the distance from the crest of one wave to the crest of the next, or between any two similar points on adjacent waves.
define and discuss: ducting
is a phenomenon where a signal propagates along the boundary of two dissimilar air masses.
define and discuss: refraction
wave that changes direction when passing from one medium to another.
define and discuss: multiplexing
simultaneous transmission of two or more signals (either in Time or Frequency) over a common carrier wave
define and discuss: modulation/demodulation
impressing intelligence upon a transmission medium/removal of intelligence from a transmission medium
define and discuss: bandwidth
the space within the radio frequency spectrum that a signal occupies, expressed in Hertz
define and discuss: keying
inserting noise or data onto a frequency
discuss the following term and give a description on what it means in relation to the atmosphere: the five main layers of the atmosphere which are determined by whether temperature increases or decreases with altitude.
highest to lowest:
exosphere
thermosphere
mesosphere
stratosphere (near constant temperature and minimal water vapor, little to no effect on radio waves.)
troposphere (almost all weather conditions occur in this layer which can greatly affect radio transmissions)

other layers to know:
ozone layer - located within stratosphere
Ionosphere - enables radio waves to be propagated to great distances around the earth making it the most important region of the atmosphere for long distance point-to-point communications.
discuss the following term and give a description on what it means in relation to the atmosphere: frequency
in the atmosphere, the higher the frequency, the more rapidly the wave will be absorbed or attenuated.
discuss the following term and give a description on what it means in relation to the atmosphere: radio waves
an elctromagnetic wave ( electromagnetic radiation ) which can be naturally occurring (lighting, astronomical objects ) or artificially generated ( radio comms, RADAR ) by a transmitter. within the atmosphere, radio waves may be reflected, refracted and diffracted.
discuss the following term and give a description on what it means in relation to the atmosphere: propagation
is the way in which waves travel. electromagnetic waves may propagate in a vacuum (space) or material medium (atmosphere). most other wave types are unable to propagate through a vacuum and require a transmission medium to exist.
discuss the following term and give a description on what it means in relation to the atmosphere: azimuth angle
in RADAR reference, it is the angle measured clockwise from true north in the horizontal plane. also called the True Bearing.
discuss the following term and give a description on what it means in relation to the atmosphere: elevation angle
in RADAR refernece, it is the angle between the horizontal plane (horizon) and the line-of-sight (LOS) - which is the direct line from the radar source to the target object.
CW Carrier Wave
in telecommunications, a carrier wave CW or carrier is a waveform which is modulated in order to convey or transmit information. in specific radio or television stations or channels, the frequency for a CW is its center frequency.
FM frequency modulation and AM amplitude modulation
FM frequency modulation and AM amplitude modulation are commonly used methods to modulate the carrier. in AM the strength (or amplitude) of the signal is varried in accordance to the instantaneous (baseline) amplitued of the modulating signal, and in FM, the CW's carrier wave's frequency is varied in accordance to the instantaneous amplitude of the modulating signal. as a result of the modulation process, a sideband, or band of frequencies containing power occurs.
USB upper side band and LSB lower side band
the signal above the CW carrier wave frequency constitutes the Upper Side Band while the signal below the CW carrier wave frequency constitutes the Lower Side Band LSB. some methods of modulation, such as single side band SSB modulation can use USB/LSB bandwidth and electrical power in a refined, more efficient manner.
define the following as it applies to radar: PRI pulse repetition interval
duration of time between the start of one pulse to the start of the next pulse, reciprocal of PRF
define the following as it applies to radar: PRF pulse repetition frequency
the rate at which pulses are transmitted, given in hertz or pulses per second, reciprocal of PRI
define the following as it applies to radar: RF radio frequency
RF energy is transmitted to and reflects from the reflecting object (target).
define the following as it applies to radar: BW beam width
describes the area of greater signal strength in the transmission pattern of the antenna (or radar).
define the following as it applies to radar: CW continuous wave
uses known, stable frequency continuous wave radio energy
define the following as it applies to radar: PW pulse width
duration of time between the leading and tailing edges of a pulse
define the following as it applies to radar: SCAN
systematic movement of a radar beam to cover a definite pattern or area in space
define the following as it applies to radar: bearing
angle measured from true north in the horizontal plane
define the following as it applies to radar: azimuth
angular measurement in the horizontal plane in a clockwise direction
define the following as it applies to radar: elevation
the angle between the horizontal plane and the light of sight (target).
Identify the following type of radar, its function, and give example: air search
detects and determines the position, course, and speed of air targets in a relatively large area:
maximum range of air-search radar can exceed 300 miles, and the bearing coverage is a complete 360 degree circle.
used as early-warning devices because they can detect approaching enemy aircraft or missiles at great distances.
Identify the following type of radar, its function, and give example: surface search
used to detect the presence of a surface craft and low flying aircraft and to determine their presence. also used extensively as a navigational aid in coastal waters in poor weather conditions.
the detection and determination of accurate ranges and bearing of surface objects and low-flying aircraft.
the maintenance of a 360 degree search pattern for all objects within line of sight distance from the radar antenna
Identify the following type of radar, its function, and give example: fire control
usually produce a vary narrow, circular beam. used to acquire targets. consists of the following three phases:
designation phase - radar is directed tot he general location of the desired target because of the narrow beam pattern.
acquisition phase - radar system searches a small volume of space in a prearranged pattern until the target is located.
tracking phase - once target is located, the radar system automatically follows all target motions. the radar system is said to be LOCKED on to the target during the track phase.
OPELINT
operationally relevant information such as the location, movement, employment, tactics, and activity of foreign non-communications emitters and their associated weapons systems.
TECHELINT
technical aspects of foreighn non-communications emitters such as signal characteristics, modes, functions, associations, capabilities, limitations, vulnerabilities, and technology levels.
HALF-DUPLEX
is a transmission mode which uses a shared transmission medium. the shared medium can be used for communications in each direction, but the communication cannot proceed simultaneously, only one at a time like walki-talkies
DUPLEX
of full-duplex, is a transmission mode which allows transmission in two directions simultaneously. example is a telephone
SIMPLEX
a simplex mechanism can only transfer data in a single direction, example, tv broadcast.