113 Technical Fundamentals Flashcards
Define ELF (3-30Hz) and what signals are used
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)
Define SLF (30-300Hz) and what signals are used
SLF (30-300Hz): SUPER LOW; common power grid frequencies (50-60Hz); U.S. and Russian deep-sea communications
Define ULF (300Hz-3Khz) and what signals are used
ULF (300Hz-3Khz): ULTRA LOW; commonly used for radio communications in mines; excellent earth-penetrating properties. Also can be used for sub communications
Define VLF (3-30Khz) and what signals are used
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.
Define LF (30-300Khz) and what signals are used
LF (30-300Khz): LOW FREQ; Fleet multichannel broadcast system. Not seriously affected during ionospheric disturbance when communications at higher frequencies are disrupted
Define MF (300Khz-3Mhz) and what signals are used
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)
Define HF (3-30Mhz) and what signals are used
HF (3-30Mhz): HIGH FREQ; mostly common used for medium & long range terrestrial radio communications
Define VHF (30-300Mhz) and what signals are used
VHF (30-300Mhz): VERY HIGH FREQ; normally used for LOS or just beyond (Amphibious operations, FM broadcasts & amateur radio communications)
Define UHF (300Mhz-3Ghz) and what signals are used
UHF (300Mhz-3Ghz): ULTRA HIGH FREQ; LOS communications (tactical voice transmissions)
Define SHF (3-30Ghz) and what signals are used
SHF (3-30Ghz): SUPER HIGH FREQ; radar and satellite communications (normally used for LOS or just beyond)
Define EHF (30-300Ghz) and what signals are used
EHF (30-300Ghz) EXTREMELY HIGH FREQ; radio astronomy. Experimental stage
What is frequency?
of cycles that occur in one second (usually in hertz)
What is a wavelength?
The physical distance of a wave or cycle; (one 360 degree cycle)
Define ducting
Temperature or moisture conditions in atmosphere that allow a greater bending of radio waves
Define refraction
Wave that changes direction when passing from one medium into another
What is multiplexing?
For simultaneous transmission of two or more signals (either in time or frequency)
Define modulation
Impressing intelligence upon a transmission medium
Define demodulation
Extraction of intelligence upon a transmission medium
What is bandwidth?
Space within the radio frequency spectrum that a signal occupies