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Questions and Answers
What is the purpose of the SELCAL system?
What is the purpose of the SELCAL system?
What happens when an aircraft receives both direct and reflected waves?
What happens when an aircraft receives both direct and reflected waves?
What is the maximum range of a VHF signal transmitted from an aircraft flying at 12000 ft received by another aircraft flying at 9000 ft?
What is the maximum range of a VHF signal transmitted from an aircraft flying at 12000 ft received by another aircraft flying at 9000 ft?
What is the primary use of HF communication?
What is the primary use of HF communication?
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What is the term for the distance between any two successive ground reflections?
What is the term for the distance between any two successive ground reflections?
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What type of wave is used for short-range communication in HF?
What type of wave is used for short-range communication in HF?
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What is the purpose of the SELCAL system?
What is the purpose of the SELCAL system?
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What is the duration of each pulse in the SELCAL system?
What is the duration of each pulse in the SELCAL system?
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What is the function of the decoder in the SELCAL system?
What is the function of the decoder in the SELCAL system?
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Which of the following is NOT a component of the SELCAL system?
Which of the following is NOT a component of the SELCAL system?
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What is the purpose of the 'RED x' code in the SELCAL system?
What is the purpose of the 'RED x' code in the SELCAL system?
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What is the primary purpose of the coupler in a HF communication system?
What is the primary purpose of the coupler in a HF communication system?
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What is the frequency of the 'RED A' tone in the SELCAL system?
What is the frequency of the 'RED A' tone in the SELCAL system?
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What is the reason for loss of voice communication in certain circumstances?
What is the reason for loss of voice communication in certain circumstances?
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How does the SELCAL system reduce unnecessary audio signals?
How does the SELCAL system reduce unnecessary audio signals?
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What type of radio system is most suitable for high frequency communication?
What type of radio system is most suitable for high frequency communication?
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What is the purpose of the Tone Selector in the SELCAL system?
What is the purpose of the Tone Selector in the SELCAL system?
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What is the purpose of the frequency and power control panel in a HF communication system?
What is the purpose of the frequency and power control panel in a HF communication system?
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What is the role of the flight interphone system in a HF communication system?
What is the role of the flight interphone system in a HF communication system?
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What is the purpose of the SELCAL system in a HF communication system?
What is the purpose of the SELCAL system in a HF communication system?
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Study Notes
Radio Frequency (RF) Communication
- RF signals travel between transceiver and antenna on a RF-Coax line
- De-modulated audio is guided to the flight interphone system for voice communications and to SELCAL for signalling purpose
- Flight recorder system receives analog pulse to signify that the transmission has been acknowledged
- In certain circumstances, the aircraft may receive both direct and reflected waves, causing fading or even short-term loss of voice communication
VHF Communication
- Maximum range of a VHF signal transmitted from an aircraft flying at 12000 ft can be received by another aircraft flying at 9000 ft, calculated as: Range = 1.25 × (9000 + 12000) = 255 nm
High Frequency (HF) Communication
- HF communication is used for long-range air-to-air and air-to-ground voice communications
- Ionospheric reflection is used for long-range HF transmission
- Factors affecting the range of HF transmission include:
- Transmission power at aircraft and ground station
- Time of day
- Season of the year
- Ionospheric disturbances
- Geographical location
- Frequency in use
- A HF communications system consists of:
- Frequency and Power control panel
- Transceiver
- Coupler (matching network for antenna)
- SELCAL system allows pilots to mute the receiver until ATC transmits a group of two pulses
SELCAL System
- SELCAL system allows pilots to receive selective calling signals
- Each aircraft is allocated a specific code, designated as ‘RED x’, where x is a letter corresponding to the audio frequency of the pulses transmitted
- Table 1-1 shows the SELCAL tone allocation, with frequencies ranging from 312.6 Hz to 1479.1 Hz
- SELCAL communications system consists of:
- Decoder
- Tone Selector
- Selcal Lamps/Switches
- Decoder receives audio from VHF/HF transceiver and decodes the signal to alert the pilot
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Description
This quiz covers the basics of radio frequency signals and communication systems in aircraft, including transmission and reception of signals, and the role of various components like transceivers and antennas.
