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Questions and Answers
HF communication relies on ____ waves for short range and ____ waves for long range.
HF communication relies on ____ waves for short range and ____ waves for long range.
ground, sky
Which of the following is NOT a factor affecting the range of HF transmission?
Which of the following is NOT a factor affecting the range of HF transmission?
- Season of the year
- Transmission power
- Aircraft altitude (correct)
- Time of day
What is the primary use of HF communication in aeronautical communications?
What is the primary use of HF communication in aeronautical communications?
Air traffic control
Sky wave communication is highly reliable and does not require frequency adjustments.
Sky wave communication is highly reliable and does not require frequency adjustments.
Match the components of a HF communication system with their corresponding function:
Match the components of a HF communication system with their corresponding function:
What is the name of the area where HF signals cannot be received due to ground reflections?
What is the name of the area where HF signals cannot be received due to ground reflections?
What type of radio system is best suited for high frequency communication?
What type of radio system is best suited for high frequency communication?
HF communication can be used for air-to-air and air-to-ground voice communications.
HF communication can be used for air-to-air and air-to-ground voice communications.
Which of the following frequencies corresponds to RED 'E' in the SELCAL tone allocation?
Which of the following frequencies corresponds to RED 'E' in the SELCAL tone allocation?
The SELCAL communications system includes a Decoder, Tone Selector, and Communication Switch.
The SELCAL communications system includes a Decoder, Tone Selector, and Communication Switch.
What is the primary function of an Emergency Locator Transmitter (ELT)?
What is the primary function of an Emergency Locator Transmitter (ELT)?
The SELCAL communications system activates an __________ in the cockpit when the relevant code is received.
The SELCAL communications system activates an __________ in the cockpit when the relevant code is received.
What is the purpose of the tone selector in the SELCAL communications system?
What is the purpose of the tone selector in the SELCAL communications system?
Match the following RED designations with their corresponding frequencies (Hz):
Match the following RED designations with their corresponding frequencies (Hz):
The ELT-RESCU 406 is a type of Selcal Lamp used in aircraft.
The ELT-RESCU 406 is a type of Selcal Lamp used in aircraft.
What happens when the crew receives an ELT activation signal?
What happens when the crew receives an ELT activation signal?
What frequency is used for military emergency locator transmitters?
What frequency is used for military emergency locator transmitters?
The maximum liquid level for ELT operation is indicated at 20,000 feet.
The maximum liquid level for ELT operation is indicated at 20,000 feet.
What is the purpose of the antenna in the ELT system?
What is the purpose of the antenna in the ELT system?
The frequency used for civil emergency locator transmitters is ______ MHz.
The frequency used for civil emergency locator transmitters is ______ MHz.
Match the following components with their function in an ELT system:
Match the following components with their function in an ELT system:
What is the primary function of the SELCAL system during long haul flights?
What is the primary function of the SELCAL system during long haul flights?
SELCAL codes are designated with a sequence of three pulses.
SELCAL codes are designated with a sequence of three pulses.
What are the two components of the pulses transmitted by the SELCAL system?
What are the two components of the pulses transmitted by the SELCAL system?
The SELCAL system allows pilots to mute the receiver until ATC transmits a series of pulses designated as ‘_____ x’.
The SELCAL system allows pilots to mute the receiver until ATC transmits a series of pulses designated as ‘_____ x’.
Match the following components with their usage in an HF communication system:
Match the following components with their usage in an HF communication system:
Which part of the SELCAL system corresponds specifically to the aircraft's listening frequency?
Which part of the SELCAL system corresponds specifically to the aircraft's listening frequency?
HF Sky Wave communication is primarily utilized for domestic flights.
HF Sky Wave communication is primarily utilized for domestic flights.
How does the SELCAL system help reduce fatigue for pilots?
How does the SELCAL system help reduce fatigue for pilots?
What is not a factor affecting the range of VHF transmission?
What is not a factor affecting the range of VHF transmission?
The transceiver is a component of the VHF communication system.
The transceiver is a component of the VHF communication system.
What is the purpose of the flight interphone system in a VHF communication system?
What is the purpose of the flight interphone system in a VHF communication system?
An aircraft transmitting at _____ ft would have its signals received by another aircraft at a lower altitude.
An aircraft transmitting at _____ ft would have its signals received by another aircraft at a lower altitude.
Match the VHF system components with their functions:
Match the VHF system components with their functions:
Which component guides de-modulated audio to the flight interphone system?
Which component guides de-modulated audio to the flight interphone system?
Fading in VHF communication can occur due to receiving both direct and reflected waves.
Fading in VHF communication can occur due to receiving both direct and reflected waves.
What happens when a transmission is acknowledged in a VHF communication system?
What happens when a transmission is acknowledged in a VHF communication system?
Which frequency is used for military rescue signals by the RESCU 406 beacon?
Which frequency is used for military rescue signals by the RESCU 406 beacon?
The RESCU 406 beacon can only operate on land and cannot function in water.
The RESCU 406 beacon can only operate on land and cannot function in water.
What is the normal emission duration of the ELT?
What is the normal emission duration of the ELT?
The RESCU 406 beacon is powered by a battery that works even in __________.
The RESCU 406 beacon is powered by a battery that works even in __________.
Match the components of the RESCU 406 beacon with their functions:
Match the components of the RESCU 406 beacon with their functions:
During land operation, what must be done to activate the water switch?
During land operation, what must be done to activate the water switch?
An ELT can only operate with fresh water for its activation.
An ELT can only operate with fresh water for its activation.
What is the rating of the Nickel-Cadmium battery mentioned for the ELT?
What is the rating of the Nickel-Cadmium battery mentioned for the ELT?
Flashcards
HF Communication
HF Communication
High Frequency communication uses 2-22 MHz for voice transmission.
Ground Wave
Ground Wave
A low-frequency wave that travels along the surface of the earth.
Sky Wave
Sky Wave
A high-frequency wave that reflects off the ionosphere for long ranges.
Skip Zone
Skip Zone
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Factors Affecting Range
Factors Affecting Range
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Transceiver
Transceiver
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Coupler
Coupler
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Ionospheric Reflection
Ionospheric Reflection
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VHF Transmission Range Factors
VHF Transmission Range Factors
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Transmission Power
Transmission Power
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Antenna
Antenna
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VHF Communications System Components
VHF Communications System Components
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RF-Coax Line
RF-Coax Line
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Fading
Fading
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Flight Recorder System
Flight Recorder System
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Height of Receiver
Height of Receiver
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SELCAL Tones
SELCAL Tones
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RED 'A' Frequency
RED 'A' Frequency
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RED 'B' Frequency
RED 'B' Frequency
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Decoder in SELCAL
Decoder in SELCAL
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Tone Selector
Tone Selector
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SELCAL Alarms
SELCAL Alarms
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Emergency Locator Transmitter (ELT)
Emergency Locator Transmitter (ELT)
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ELT-RESCU 406
ELT-RESCU 406
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RESCU 406
RESCU 406
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Rescue signals
Rescue signals
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Civil Rescue Frequency
Civil Rescue Frequency
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Military Rescue Frequency
Military Rescue Frequency
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Water Operation
Water Operation
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Land Operation
Land Operation
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Liquid Activation
Liquid Activation
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Normal Emission Duration
Normal Emission Duration
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Ionosphere
Ionosphere
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HF/Sky Wave
HF/Sky Wave
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HF/Ground Wave
HF/Ground Wave
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SELCAL
SELCAL
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Receiver Noise
Receiver Noise
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Transmitter Pulses
Transmitter Pulses
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Control Panel Inputs
Control Panel Inputs
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121.5 MHz Frequency
121.5 MHz Frequency
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243 MHz Frequency
243 MHz Frequency
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ELT Water Operation
ELT Water Operation
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ELT Land Operation
ELT Land Operation
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Study Notes
VHF/HF Communication Systems
- VHF communication is line-of-sight, short-range air-to-air and air-to-ground communication.
- Primarily used for air traffic control in the 118-136 MHz band.
- Range is estimated by a formula: R = 1.25 (√Hr + √Ht), where R is in nautical miles, and Hr and Ht are receiver and transmitter antenna heights above Mean Sea Level (MSL).
- Factors affecting VHF range include transmission power, antenna height, receiver height and obstacles.
- A VHF communication system consists of frequency control panel, transceiver and antenna.
High Frequency (HF) Communication
- HF communication uses ground waves for short range and sky waves for long range, enabling air-to-air and air-to-ground voice communication.
- Primarily used for air traffic control in the 2-22 MHz band.
- Range depends on ionospheric reflection, potentially requiring multiple bounces.
- Skip zone refers to the distance between successive ground reflections. This is useful for selecting appropriate frequencies.
- Factors affecting HF range: transmission power, time of day, season, ionospheric disturbances, geographic location, and frequency.
- A typical HF communication system comprises frequency control panel, transceiver, and antenna coupler.
Selective Calling System (SELCAL)
- SELCAL allows pilots to mute their radios, except when they are called.
- ATC transmits a series of pulses (RED x) with distinct audio frequencies.
- Each code (RED x) is assigned to a specific aircraft.
- These pulses modulate the carrier frequency. The receiver system decodes the signal and alerts the pilot to the message.
Emergency Locator Transmitter (ELT)
- ELTs are radio devices that activate in emergencies, aiding in locating crash sites and survivors.
- ELT-RESCU 406 is an example, transmitting two kinds of signals for civil and military rescue.
- The device includes various parts like batteries, antenna, lanyard, plastic water bag.
- The ELT operates for a duration of 48 hours, transmitting distinctive frequencies.
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Description
Explore the principles of VHF and HF communication systems, focusing on their applications in air traffic control. Learn about the range estimation formulas and factors that affect communication quality in aviation. This quiz will test your understanding of both VHF and HF technologies.
