This set of Aircraft Maintenance Multiple Choice Questions & Answers (MCQs) focuses on “Radio Shop – VHF”.
1. Which is the only channel that retains 100 kHz channel spacing in the US?
a) 121.5 MHz
b) 131.5 MHz
c) 141.5 MHz
d) 171.5 MHz
View Answer
Explanation: 121.5 MHz is the only channel that retains 100 kHz channel spacing in the US. It is an emergency communication channel. No channel allocations are present between 121.4 and 121.5 or between 121.5 and 121.6.
2. What is the transmission range of an aircraft flying at a cruise altitude of 35,000 feet?
a) 2000 mi
b) 400 mi
c) 200 mi
d) 4000 mi
View Answer
Explanation: The transmission range of an aircraft flying at a cruise altitude of 35,000 feet, is roughly around 200 miles, which is approximately 322 km. The range is dependent on the prevailing weather conditions and is reduced in extreme weather conditions.
3. The VHF air band uses the frequencies between 108 and ___________ MHz.
a) 127
b) 137
c) 110
d) 237
View Answer
Explanation: The VHF air band uses the frequencies between 108MHz and 137MHz. In most countries a license is required to operate an air band equipment.
4. Which of the following is not true about VHF propagation?
a) Can penetrate building walls
b) Can travel long distances
c) Transmitting antennas are huge
d) Can be received indoors
View Answer
Explanation: VHF band is the first band which offers transmitting antennas small enough that they can be mounted on vehicles and portable devices. The VHF signals can be received indoors and are able to travel long distances if conditions are suitable.
5. Which of the following is not a common use for radio waves in the VHF band?
a) FM radio broadcasting
b) Walkie-talkie communication
c) Marine communications
d) Television broadcasting
View Answer
Explanation: Walkie-talkie communication is not a common use for radio waves in the VHF band. However, FM radio broadcasting, Marine communications and Television broadcasting are all common uses of radio waves in the VHF band.
6. Frequencies lying immediately below VHF are referred to as _________
a) High frequency
b) Ultra high frequency
c) Low frequency
d) Ultra low frequency
View Answer
Explanation: Frequencies lying immediately below VHF are referred to as high frequency. The high frequency band has a number of applications ranging from aviation communication, weather analysis and government usage. Further, the high frequency band succeeds the medium frequency band.
7. What is the frequency range of VHF (Very high frequency)?
a) 30 MHz to 300 MHz
b) 30 Hz to 300 Hz
c) 30 KHz to 300 KHz
d) 30 mHz to 300 mHz
View Answer
Explanation: Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. VHF is the ITU designation for the range of radio frequency EM Waves.
8. When were the frequencies between 136.000 and 136.975 MHz added?
a) 1 January 2019
b) 1 January 2010
c) 1 January 1990
d) 1 January 1999
View Answer
Explanation: The frequencies lying between the 136.000 and 136.975 MHz bandwidth were added on 1 January 1990. These frequencies helped in increasing the total number of channels to 740. The addition was necessary to decrease the load on the existing channels.
9. Radio operations used for aircraft communication make use of ___________
a) Amplitude modulation
b) Frequency modulation
c) Phase modulation
d) Channel Modulation
View Answer
Explanation: Radio operations used for aircraft communication make use of amplitude modulation techniques. It is a reliable modulation technique and ensures that the signal is transmitted with minimal loss.
10. Military aircraft also use a dedicated UHF-AM band from 225.0–399.95.
a) False
b) True
View Answer
Explanation: True, military aircraft also use a dedicated UHF-AM band from 225.0–399.95. It is used mainly for air-to-air and air-to-ground communications, including communications with the ATC.
11. What is the full form of SSB modulation?
a) Shaky-sideband modulation
b) Separated-sideband modulation
c) Sorted-sideband modulation
d) Singe-sideband modulation
View Answer
Explanation: SSB modulation refers to Singe-sideband modulation (SSB), or single-sideband suppressed-carrier modulation (SSB-SC). Under SSB modulation, the transmitter bandwidth and power are used in a more efficient manner and the system is based on AM Modulation.
12. What is the maximum audio frequency at which an air band channel can operate?
a) 4.166 MHz
b) 4.166 mHz
c) 4.166 kHz
d) 4.166 Hz
View Answer
Explanation: The maximum audio frequency at which an air band channel can operate is 4.166 kHz. The frequency is kept in accordance to the largest possible bandwidth of a particular air band channel, which is 8.33 kHz.
13. The European Union allows a maximum of ___________ air band channels.
a) 2,280
b) 280
c) 774
d) 228
View Answer
Explanation: The European Union allows a maximum of 2,280 air band channels. Further, it is a common practice in the European Union to divide one air band channel into three different channels, thus increasing the total available channels.
14. Which of the following is the emergency channel for military aircraft?
a) 243.0 Hz
b) 243.0 MHz
c) 343.0 MHz
d) 343.0 Hz
View Answer
Explanation: 243.0 MHz is the emergency channel for military aircraft. The channel also serves as a guard channel but is typically designated for emergency situations.
15. The lowest 10 MHz of the band is split into narrow-band channels of 50 kHz.
a) False
b) True
View Answer
Explanation: True, the lowest 10 MHz of the band is split into narrow-band channels of 50 kHz. The band from 108–117.95 MHz, is split into 200 narrow-band channels of 50 kHz.
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