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113
Technical Fundamentals
| Question | Answer |
|---|---|
| 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 |