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113

Technical Fundamentals

QuestionAnswer
ELF ( Extremely Low Frequencies) 3-30 Hz Penetrate ocean depths
SLF (Super Low Frequencies) 30-300 Hz AC power grids
ULF (Ultra Low Frequencies) 300-3000 Hz Used by military for secure comms through the ground
VLF (Very low Frequency) 3-30 kHz communications or navigation
LF ( Low Frequency) 30-300 kHz radio comms
MF (Medium Frequency) .0303 MHz international distress frequencies
HF (High Frequency) 3-30 MHz point-to-point, ship-to-shore
VHF (very high frequency) 30-300 MHz bounce of the atmosphere
UHF (ultra high frequency) 0.3-3 GHz line of sigh communications
SHF (Super High Frequency) 3-30 GHz radar and satellite comms
EHF (extremely high frequency) 30-300 GHz experimental stages
Frequency number of cycles per unit of time
Wavelength distance in space occupied by one cycle of a radio wave at any given instant
Ducting bending of the radar waves passing through the abnormal condition
Refraction bending of electromagnetic waves caused by a change in the density of the medium
Multiplexing simultaneous transmission of 2 or more signals over a common carrier wave
Modulation/ Demodulation impress intelligence upon a transmission medium Demodulation- removing intelligence form the medium
Bandwidth difference between the highest usable frequency of a device and the lowest usable frequency of the device
Keying shift between 2 differing frequencies by opening and closing a key
3 Layers of the Earth's atmosphere Troposphere, Stratosphere, Ionosphere
Frequency relation to atmosphere for any given time, each ionosphere layer has a maximum frequency at which radio waves can be transmitted vertically and refracted back to earth's surface
Radio Wave relation to atmosphere 2 principal ways in which EM energy travels from a transmitting antenna to a receiving antenna. Ground Waves- near the surface of Earth Sky Waves- reflected back to Earth from ionosphere
Propagation relation to atmosphere transmissions of a wave through a medium
Azimuth angle relation to atmosphere horizontal angle degree
Elevation angle relation to atmosphere angle between the horizontal and the line from the object to observer's eve
USB modulation upper sideband is all of the sum frequencies above the carrier
LSB modulation lower sideband is frequencies below that of the carrier
CW modulation "on-off" keying of a continuous wave carrier frequency
Amplitude Modulation (AM) varying the amplitude of an EM carrier frequency
Frequency Modulation (FM) angle modulation which causes the carrier frequency to vary
How does Pulse Repetition Interval (RPI) apply to RADAR? interval between the start on one pulse and the start of the next pulse
How does Pulse Repetition Frequency (PRF) apply to RADAR? the rate at which pulses are transmitted, given in Hz/ pulse per second
How does Radio Frequency (RF) apply to RADAR? energy is transmitted to and reflects from the reflecting object
How does Beam Width (BW) apply to RADAR? width of a radar beam measured between half points
How does Doppler Effect apply to RADAR? a shift and change in frequency
How does Pulse Width (PW) apply to RADAR? duration of time between the leading and trailing edges of a pulse
How does scan apply to RADAR? movement of a radar beam while searching for or tracking a target
how does Bearing apply to RADAR? referenced to true North
How does azimuth apply to RADAR? horizontal plane in a clockwise direction
How does elevation apply to RADAR? line of sight
Air Search Radar determine the position, course, and speed of air targets
Surface Search Radar the detection of surface objects
Fire Control Radar positional data on a target
Difference between OPELINT and TECHELINT OPELINT- concerned with operationally relevant information TECHELINT- concerned with technical aspects of foreign non-communications emitters
Half- Duplex (HDX) 1 way cannot send/receive
Full Duplex (FDX) 2 way can receive/send messages
Simplex (SPLX) 1 direction Uses a single channel to exchange information between 2 or more terminals