What is amplitude
More energy a wave is carrying the more amplitude it has
What is wavelength
Distance of a complete wave cycle (usually peak-peak or trough-trough)
What is Frequency
- Number of wave cycles per unit of time
- Hz = Waves/sec
- Higher frequency transmits more info faster
What is the HF Frequency Band
HF = 1.600-29.999 MHz
What is the VHF frequency band
VHF = 30.000-224.999 MHz
What is the UHF frequency band
225.000-3,000 MHz (3GHz)
What are the UHF propagation characteristics and what is it used for?
- Line of sight propagation
- Forward Air Control (FAC)
- LOS Comms
What are HF propagation characteristics, range and uses?
- Long and short range secure voice and data comms
- Range: 30km man pack / 100km vehicle
- Ground wave and Sky wave propagation (over the horizon)
- Sky wave: ionosphere bounce w/ skip zone
- Ground wave: decreased range with vegetation, mountains, dry desert
What is a net and what is net control
Net: a frequency and all stations using it.
Net Control: station responsible for managing traffic on that net
What are the Transmission Power Levels & Ranges?
- LO (manpack/vehicular lo) 200-400m
- M (medium) 400m-5km
- Hi (high) 5-10km
- PA (power amplified) 10-40km
What is critical LOS or optical LOS
Two antennas need to be able to “see” each other to function. Applies to UHF. Waves reflect which may benefit in MOUT
What are the data transmission speeds for UHF and HF
UHF: up to 16kbps
HF: up to 2.4kbps
What are vulnerabilities of UHF
- Absorbed by foliage (decreased range)
- Vulnerable to radio direction finding (RDF)
- Usually poor performance in rural areas
What is the primary MAGTF VHF Radio
- Single Channel Ground and Airborne Radio System (SINCGARS)
- Uses frequency hopping, integrated COMSEC
VHF Characteristics and Planning Factors
- “radio LOS” instead of optical or critical
- Diffracts around curvature of the earth but much less than HF
- Absorbed by foliage but less than UHF
- Good performance in rural areas
- vulnerable to accurate RDF
HF Characteristics and Planning Factors
- Capable of long & short range secure voice and data comms
- Data comms are very slow: 2.4kbps
- Modem must be designed for ops in this band
What are the 3 types of HF Sky waves
- Near Vertical Incidence Skywave (NVIS) near 90 degree
- Medium-Haul skywave approx 50 degree
- Long-Haul skywave approx 20 degree
HF disadvantages/limitations
- Slow data rate
- can be intercepted/traced by enemies 100s of miles away
- limited bandwidth
- solar storms can eliminate HF
What bands do single channel radios (SCR) work in?
- HF
- VHF
- UHF
- UHF-tactical satellite (TACSAT)
What are the benefits of frequency hopping
- Prevents enemy from jamming or locking on to a freq
What is the channel spacing and timing for frequency hopping?
- 25 KHz channel spacing
- all radios must be synch’d within 4 seconds
What is a Hopset?
The set of frequencies on which an FH net hops
What is the difference between plain text and cipher text?
- Plain text: uncovered
- Cypher text: covered/encrypted
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Written Practice Test80
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FMF Written Practice Tests0
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Section 103 Safety10
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Section 101 USMC History, Customs, and Courtesies44
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Section 102 USMC Mission and Organization30
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Section 104 Administrative Fundamentals18
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Section 105 ACE63
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Section 106 GCE58
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Section 107 LCE42
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Section 108 CE14
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Section 109 Amphibious Ops23
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Section 110 Force Protection15
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Section 111 Gen Combat Leadership15
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Section 112 USMC Ops20
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Section 113 Environmental Awareness5
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Section 114 Communications23
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Section 115 Weapons10
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Section 116 Tactical Measures16
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Section 117 Land Nav29
