CDC Vol 1, 016 Radio Frequency Bands and Uses Flashcards
- What band of frequencies do we know as the HF band?
From 3 to 30 MHz.
- Which frequencies are in high demand because of their reliable long-range propagation accommodating voice and teletype data?
High frequency.
- Are frequencies in the VHF range useful for long-distance communications? Explain.
No. Frequencies in the VHF range and above are limited to line of sight; that is, they are not normally reflected by the ionosphere.
- What are the three principal methods of UHF propagation?
- LOS
- Troposheric scatter
- Satellite
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Why is HF affected by the time of day?
The sun affects the ionosphere. Therefore, HF will respond differently at different times of the day.
What is the frequency range of HF, VHF, and UHF?
- HF 3-30 MHz
- VHF 30-300 MHz
- UHF 300-3000 MHz
What can VHF accommodate due to the relatively greater spectrum space?
Emissions using wide bandwidths
What does VHFs ability to use directional antennas that can be beamed sharply to from point-to-point provide?
Additional security
What part of the atmosphere does HF propagate?
Ionosphere
What is the principal methods of UHF propagation?
- LOS
- Troposheric scatter
- Satellite
Depending on weather and other variables, what is the LOS range of air-to-ground assets?
200+ NM
What term refers to the scattering of radio signals by bouncing them off the lower portion of the earth’s atmosphere?
Troposcatter also called Troposheric scatter
When would ground unites use troposcatter propagation for UHF?
- Two locations are so far apart the Earth’s curvature prevents LOS communications.
- When geographical obstructions prohibit LOS.
What is the range of ground-to-ground units using UHF troposcatter propagation?
200+ NM
How many miles above the earth does a satellite need to be at to stay in a geosynchronous orbit?
22,279 miles
How far can two units be from each other and still use the same satellite for communication?
8,400 miles
Essentially, what is a satellite in SATCOM?
A microwave link repeater
What are the three elements necessary to defeat jamming?
- Common Frequencies
- Time Synchronization
- Common Hopping Pattern and Rate
In HAVE QUICK, what determines the hopping pattern/rate and ensures all systems users have a common time base?
- WOD determines Hopping patter
- TOD provides timing
What is TOD commonly refered to?
Mickey
What is a multi-digit code common worldwide to all HAVE QUICK users?
WOD - Word-of-day
