Eidws Common Core 113

Front 1

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: extremely low frequency ELF

Back 1

3-30Hz, long range signals, subs operating BEYOND NORMAL MISSION DEPTH. rarely used due to extremely large antenna required

Front 2

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Super Low Frequency SLF

Back 2

common power grids freqs (50-60 Hz) us and russian deep sea coms

Front 3

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Ultra Low Frequency ULF

Back 3

300Hz-3Khz commonly used for radio coms in mines, excellent earth-penetrating properties. also can be used for sub coms

Front 4

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Very Low Frequency VLF

Back 4

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

Front 5

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Low Frequency LF

Back 5

30Khz - 300Khz fleet multi-channel broadcast system.

Front 6

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Medium Frequency MF

Back 6

300Khz - 3Mhz primarily by navy for ground wave transmissions. commercial AM broadcasts, includes international distress freqs.

Front 7

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: High Frequency HF

Back 7

3-30 Mhz most commonly used for medium and long range terrestrial radio coms

Front 8

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Very High Frequency VHF

Back 8

30 300Mhz normally used for LOS of just beyond

Front 9

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Ultra High Frequency UHF

Back 9

300Mhz - 3 Ghz LOS comms, tatical voice transmissions

Front 10

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Super High Frequency SHF

Back 10

RADAR AND SATELLITE COMMS normally used for LOS or just beyond

Front 11

define this band of the electromagnetic spectrum and describe what signals are commonly used in it: Extremely High Frequency EHF

Back 11

30 - 300Ghz radio astronomy, experimental stage

Front 12

define and discuss: frequency

Back 12

the number of cycles that occur in one second. usually expressed in hertz

Front 13

define and discuss: wavelength

Back 13

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.

Front 14

define and discuss: ducting

Back 14

is a phenomenon where a signal propagates along the boundary of two dissimilar air masses.

Front 15

define and discuss: refraction

Back 15

wave that changes direction when passing from one medium to another.

Front 16

define and discuss: multiplexing

Back 16

simultaneous transmission of two or more signals (either in Time or Frequency) over a common carrier wave

Front 17

define and discuss: modulation/demodulation

Back 17

impressing intelligence upon a transmission medium/removal of intelligence from a transmission medium

Front 18

define and discuss: bandwidth

Back 18

the space within the radio frequency spectrum that a signal occupies, expressed in Hertz

Front 19

define and discuss: keying

Back 19

inserting noise or data onto a frequency

Front 20

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.

Back 20

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.

Front 21

discuss the following term and give a description on what it means in relation to the atmosphere: frequency

Back 21

in the atmosphere, the higher the frequency, the more rapidly the wave will be absorbed or attenuated.

Front 22

discuss the following term and give a description on what it means in relation to the atmosphere: radio waves

Back 22

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.

Front 23

discuss the following term and give a description on what it means in relation to the atmosphere: propagation

Back 23

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.

Front 24

discuss the following term and give a description on what it means in relation to the atmosphere: azimuth angle

Back 24

in RADAR reference, it is the angle measured clockwise from true north in the horizontal plane. also called the True Bearing.

Front 25

discuss the following term and give a description on what it means in relation to the atmosphere: elevation angle

Back 25

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.

Front 26

CW Carrier Wave

Back 26

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.

Front 27

FM frequency modulation and AM amplitude modulation

Back 27

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.

Front 28

USB upper side band and LSB lower side band

Back 28

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.

Front 29

define the following as it applies to radar: PRI pulse repetition interval

Back 29

duration of time between the start of one pulse to the start of the next pulse, reciprocal of PRF

Front 30

define the following as it applies to radar: PRF pulse repetition frequency

Back 30

the rate at which pulses are transmitted, given in hertz or pulses per second, reciprocal of PRI

Front 31

define the following as it applies to radar: RF radio frequency

Back 31

RF energy is transmitted to and reflects from the reflecting object (target).

Front 32

define the following as it applies to radar: BW beam width

Back 32

describes the area of greater signal strength in the transmission pattern of the antenna (or radar).

Front 33

define the following as it applies to radar: CW continuous wave

Back 33

uses known, stable frequency continuous wave radio energy

Front 34

define the following as it applies to radar: PW pulse width

Back 34

duration of time between the leading and tailing edges of a pulse

Front 35

define the following as it applies to radar: SCAN

Back 35

systematic movement of a radar beam to cover a definite pattern or area in space

Front 36

define the following as it applies to radar: bearing

Back 36

angle measured from true north in the horizontal plane

Front 37

define the following as it applies to radar: azimuth

Back 37

angular measurement in the horizontal plane in a clockwise direction

Front 38

define the following as it applies to radar: elevation

Back 38

the angle between the horizontal plane and the light of sight (target).

Front 39

Identify the following type of radar, its function, and give example: air search

Back 39

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.

Front 40

Identify the following type of radar, its function, and give example: surface search

Back 40

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

Front 41

Identify the following type of radar, its function, and give example: fire control

Back 41

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.

Front 42

OPELINT

Back 42

operationally relevant information such as the location, movement, employment, tactics, and activity of foreign non-communications emitters and their associated weapons systems.

Front 43

TECHELINT

Back 43

technical aspects of foreighn non-communications emitters such as signal characteristics, modes, functions, associations, capabilities, limitations, vulnerabilities, and technology levels.

Front 44

HALF-DUPLEX

Back 44

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

Front 45

DUPLEX

Back 45

of full-duplex, is a transmission mode which allows transmission in two directions simultaneously. example is a telephone

Front 46

SIMPLEX

Back 46

a simplex mechanism can only transfer data in a single direction, example, tv broadcast.