113 Technical Fundamentals

Question 1

Define ELF (3-30Hz) and what signals are used

Answer 1

ELF (3-30Hz): EXTREMELY LOW; long range signals subs operating beyond normal mission depth
- Lower freq: deeper signal can be received underwater (rarely used due to extreme antenna size required)

Question 2

Define SLF (30-300Hz) and what signals are used

Answer 2

SLF (30-300Hz): SUPER LOW; common power grid frequencies (50-60Hz); U.S. and Russian deep-sea communications

Question 3

Define ULF (300Hz-3Khz) and what signals are used

Answer 3

ULF (300Hz-3Khz): ULTRA LOW; commonly used for radio communications in mines; excellent earth-penetrating properties. Also can be used for sub communications

Question 4

Define VLF (3-30Khz) and what signals are used

Answer 4

VLF (3-30Khz): VERY LOW; Long range signals to subs operating at normal mission speeds & depths; crucial communications during hostilities & used as backup to communications blacked out by nuclear activity.

Question 5

Define LF (30-300Khz) and what signals are used

Answer 5

LF (30-300Khz): LOW FREQ; Fleet multichannel broadcast system. Not seriously affected during ionospheric disturbance when communications at higher frequencies are disrupted

Question 6

Define MF (300Khz-3Mhz) and what signals are used

Answer 6

MF (300Khz-3Mhz): MED FREQ; primarily by Navy for ground wave transmissions (lower portion of MF band); Commercial AM broadcasts (utilizes majority of MF range); includes international distress frequencies (500Khz/484Khz)

Question 7

Define HF (3-30Mhz) and what signals are used

Answer 7

HF (3-30Mhz): HIGH FREQ; mostly common used for medium & long range terrestrial radio communications

Question 8

Define VHF (30-300Mhz) and what signals are used

Answer 8

VHF (30-300Mhz): VERY HIGH FREQ; normally used for LOS or just beyond (Amphibious operations, FM broadcasts & amateur radio communications)

Question 9

Define UHF (300Mhz-3Ghz) and what signals are used

Answer 9

UHF (300Mhz-3Ghz): ULTRA HIGH FREQ; LOS communications (tactical voice transmissions)

Question 10

Define SHF (3-30Ghz) and what signals are used

Answer 10

SHF (3-30Ghz): SUPER HIGH FREQ; radar and satellite communications (normally used for LOS or just beyond)

Question 11

Define EHF (30-300Ghz) and what signals are used

Answer 11

EHF (30-300Ghz) EXTREMELY HIGH FREQ; radio astronomy. Experimental stage

Question 12

What is frequency?

Answer 12

of cycles that occur in one second (usually in hertz)

Question 13

What is a wavelength?

Answer 13

The physical distance of a wave or cycle; (one 360 degree cycle)

Question 14

Define ducting

Answer 14

Temperature or moisture conditions in atmosphere that allow a greater bending of radio waves

Question 15

Define refraction

Answer 15

Wave that changes direction when passing from one medium into another

Question 16

What is multiplexing?

Answer 16

For simultaneous transmission of two or more signals (either in time or frequency)

Question 17

Define modulation

Answer 17

Impressing intelligence upon a transmission medium

Question 18

Define demodulation

Answer 18

Extraction of intelligence upon a transmission medium

Question 19

What is bandwidth?

Answer 19

Space within the radio frequency spectrum that a signal occupies

Question 20

What is keying?

Answer 20

Inserting noise or data onto a frequency

Question 21

What is an Azimuth Angle?

Answer 21

Angular measurement in the horizontal plane in a clockwise direction

Question 22

What is an Elevation Angle?

Answer 22

Angle between horizontal plane and LOS (altitude)

Question 23

Discuss the Troposphere

Answer 23

Located between surface of Earth to about 3.7 miles at North Pole or South Pole and 11.2 miles at the equator

Question 24

Discuss the Stratosphere

Answer 24

Located between troposphere and ionosphere; little to no effect on radio waves

Question 25

Discuss the Ionosphere

Answer 25

Located upward from about 31.1 miles to about 250 miles; contains 4 cloud-like layers

Question 26

Discuss radio waves in relation to the atmosphere

Answer 26

Form of radiant energy that can neither be seen nor felt; electromagnetic wave generated by a transmitter

Question 27

Discuss propagation

Answer 27

Movement of a signal through a medium i.e. light rays

Question 28

Describe USB: Upper Sideband

Answer 28

The intelligence/data carrying section of a signal located adjacent to and HIGHER in frequency than the Center Frequency (CF)

Question 29

Describe LSB: Lower Sideband

Answer 29

The intelligence/data carrying section of a signal located adjacent to and LOWER in frequency than the Center Frequency (CF). The inverse (mirror) of the USB

Question 30

Describe CW: Carrier Wave

Answer 30

AKA "modulating wave"; carrier wave is the radio frequency which facilitates the transmission of intelligence across a medium

Question 31

Describe AM: Amplitude Modulation

Answer 31

Technique used in electronic communications, most frequently for transmitting information via a radio carrier wave

Question 32

Describe FM: Frequency Modulation

Answer 32

Conveys info over a carrier wave by varying its frequency

Question 33

Describe PRI (Pulse Repetition Interval) as it applies to RADAR

Answer 33

Duration of time the leading edge of one pulse to leading edge of another pulse

Question 34

Describe PRF (Pulse Repetition Freq) as it applies to RADAR

Answer 34

Rate at which pulses are transmitted (inverse of PRI)

Question 35

Describe RF (Radio Freq) as it applies to RADAR

Answer 35

Energy that is transmitted

Question 36

Describe BW (Bandwidth) as it applies to RADAR

Answer 36

The space within the RF spectrum that a signal occupies

Question 37

Describe CW (Continuous Wave) as it applies to RADAR

Answer 37

Unmodulated frequency that does not carry additional modulated intelligence

Question 38

Describe PW/PD (Pulse Width/Pulse Duration) as it applies to RADAR

Answer 38

Duration of time between the leading and trailing edge of the same pulse

Question 39

Describe Scan as it applies to RADAR

Answer 39

Systematic movement of a radar beam

Question 40

Describe Bearing as it applies to RADAR

Answer 40

Angle measured clockwise from true north in the horizontal plane

Question 41

Describe Azimuth as it applies to RADAR

Answer 41

Angular measurement in the horizontal plane in a clockwise direction

Question 42

Describe Elevation as it applies to RADAR

Answer 42

Angle between the horizontal plane and line-of-sight (altitude)

Question 43

Identify the type of RADAR: Air Search

Answer 43

Detect & determine position, course, & speed of air targets

Question 44

Identify the type of RADAR: Surface Search

Answer 44

Used to detect presence of surface craft & low flying aircraft

Question 45

Identify the type of RADAR: Fire Control

Answer 45

Produces a vary narrow, circular beam. 3 phases: - Designation Phase: Radar is directed to general location of desired target - Acquisition Phase: Radar system searches small volume of space in prearranged pattern until target is loaded - Tracking Phase: Once target located, radar system automatically follows target motions

Question 46

Explain the difference between OPELINT & TECHELINT

Answer 46

OPELINT: Operationally relevant info (location, movement, tactics) TECHELINT: Technical aspects (signal characteristics, modes, function, capabilities, vulnerabilities, & technology)

Question 47

Define Half Duplex

Answer 47

Can be used for communications in each direction, but can't proceed simultaneously i.e. walkie-talkies

Question 48

Define Duplex

Answer 48

Allows transmission in two directions simultaneously i.e. telephone

Question 49

Define Simplex

Answer 49

Can only transfer data in a single direction i.e. broadcast radio