30 Questions
What is the minimum frequency range required for the transmission of speech?
500 Hz to 2000 Hz
Why is it not practical to transmit human voice frequencies via radio circuits?
Because of the extremely long wavelengths
What is the typical range of radiating elements in antennas?
1/4, 1/2, 1, or more full wavelengths
What is the process called that impresses the voice signal onto a radiofrequency wave?
Modulation
Why is a carrier wave used in radiotelephone circuits?
To have a wavelength short enough to be radiated from an antenna of practical dimensions
What is the wavelength of the frequency 250 Hz on radiotelephone circuits?
1 200 000 meters
What is the primary factor that affects the range of HF communications?
Frequency selected and time of day
Why do HF transmitters produce a higher output power compared to VHF transmitters?
To achieve longer communication ranges
What is the primary reason why jet aircraft rarely have long wire HF antennas?
Vibration and increased risk of damage at high speeds
Why do long wire antennas on light aircraft have a weak point?
To prevent the antenna from wrapping around the aircraft and causing damage
What is the maximum range of VHF communications?
About 400 km (air to ground)
Why do aircraft sometimes lose communication over the middle of an ocean?
Due to atmospheric interference from thunderstorms
What is the primary purpose of the ARINC Control and Reporting System (ACARS) in aircraft operations?
To reduce reliance on voice communications for routine information transmission
What system is used by the aircraft to transmit data to the Airline Operations Controllers (AOC) facilities?
VHF radio system
What is the purpose of the ACARS computer on the aircraft?
To receive and demodulate the ACARS encoded data from the VHF radio system
What is the benefit of using ACARS in terms of aircraft turnaround planning?
It enables more efficient planning of logistics support
What type of information is typically transmitted between the aircraft and Airline Operations Controllers (AOC) using ACARS?
Routine information such as aircraft status and logistics requirements
What organization developed and implemented the ARINC Control and Reporting System (ACARS)?
Aeronautical Radio Incorporated (ARINC)
What happens to the receiver function when the push-to-transmit button is pressed?
It is replaced by the transmitter function
Why are two separate receiver/transmitter systems required for full duplex transmission?
To allow simultaneous transmission and reception
What is a characteristic of radio transmissions?
They can be received by any radio receiver within the broadcast area
What is the function of the radio control panel?
To interface system components and control radio system functions
What is normally remotely located on the control column?
The press-to-transmit button
What is displayed on the radio control panel?
The carrier frequency being modulated by the audio
What is the primary function of the Management Unit in an ACARS system?
To control the transmission and reception of air-to-ground and ground-to-air messages
What type of signal is formatted by the Management Unit for transmission to the ground?
Digital
What is the purpose of the Control Unit in an ACARS system?
To allow the flight crew to enter information into the data link system
What type of messages are typically printed out by the printer in an ACARS system?
Weather reports and dispatch messages
What is the term for the radio transmission path upward from the earth to the aircraft?
Uplink
What triggers the Management Unit to collect data from the Control Unit and various aircraft systems?
Clearing the gate and being ready to taxi
Test your knowledge of the frequency ranges used in speech transmission, including the minimum range required for speech transmission and the average range used on radiotelephone circuits. Learn about the challenges of transmitting human voice frequencies over radio circuits.
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