Aircraft Maintenance Questions and Answers – Aviation Communication Systems – DME-2

This set of Aircraft Maintenance Multiple Choice Questions & Answers focuses on “Aviation Communication Systems – DME-2”.

1. The physical distance between the aircraft antenna and the DME transponder antenna is referred to as _________
a) Slant range
b) Slant height
c) Slant angle
d) Slant length

Explanation: The physical distance between the aircraft antenna and the DME transponder antenna is referred to as slant range. It is measured using the DME.

2. The spacing of all channels is 1 Hz.
a) False
b) True

Explanation: False, the spacing of all channels is 1 MHz. Further, it has a signal spectrum width of 100 kHz. There are 126 channels each, for interrogation and reply.

3. The typical DME ground based responder beacon has a limit of ________ interrogations per second.
a) 2700
b) 270
c) 27
d) 27000

Explanation: The typical DME ground based responder beacon has a limit of 2700 interrogations per second. It refers to pulse pairs per second, called pps.

4. Which of the following frequencies are used by an airplane’s DME interrogator?
a) 1025 mHz to 1150 mHz
b) 1025 Hz to 1150 Hz
c) 1025 MHz to 1150 MHz
d) 1025 KHz to 1150 KHz

Explanation: 1025 MHz to 1150 MHz are the frequencies are used by an airplane’s DME interrogator. DME frequencies are paired to VHF omnidirectional range frequencies.

5. Which of the following is the range of frequency for the transmitting channel of DME transponders?
a) 962 mHz to 1213 mHz
b) 962 Hz to 1213 Hz
c) 962 KHz to 1213 KHz
d) 962 MHz to 1213 MHz

Explanation: 962 MHz to 1213 MHz is the range of frequency for the transmitting channel of DME transponders. The range frequency for the receiving channel is between 1025 and 1150 MHz.

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6. How much is the difference between interrogation and reply frequencies?
a) 63 MHz
b) 63 Hz
c) 60 MHz
d) 63 Hz

Explanation: The difference between a pair of interrogation and reply frequencies is of the magnitude of 63 MHz. Also the band comprises of 126 channels solely for interrogation purpose and another 126 channels for reply purposes.

7. DME facilities use a ___________ Morse code in order to identify themselves.
a) 1,350 MHz
b) 1,350 Hz
c) 150 Hz
d) 150 MHz

Explanation: The DME use a 1,350 Hz Morse code in order to identify themselves. This code is in the form of a three letter identity, which when collated with either a VOR or ILS system, will have a similar identity code.

8. Terminal transponders generally work to a minimum height above ground of ________
a) 12,000 feet
b) 1200 feet
c) 120 feet
d) 12 feet

Explanation: Terminal transponders generally work to a minimum height above ground of 12,000 feet. These transponders are usually installed in airport buildings. Such transponders often have a short range and are unable to work in extreme weather conditions.

9. What is the range of high altitude transponders?
a) 1300 nautical miles
b) 13 nautical miles
c) 100 nautical miles
d) 130 nautical miles

Explanation: The range of high altitude transponders is 130 nautical miles. They typically provide service to a minimum height of 45,000 feet. These devices are based on wireless communication and can operate in extreme conditions.

10. How many frequencies are defined for DME interrogations and replies?
a) 25
b) 2520
c) 252
d) 22

Explanation: A total of 252 frequencies are defined for DME interrogations and replies. However, all of them are not used. The frequencies are the same for X and Y channels.

11. X channels have both interrogation and reply pulse pairs spaced by 12 microseconds.
a) False
b) True

Explanation: True, the X channels have both interrogation and reply pulse pairs spaced by 12 microseconds. This separation is not the same for Y channels.

12. The Y channels interrogation pulse pairs are spaced by __________
a) 36 milliseconds
b) 36 seconds
c) 36 microseconds
d) 36 nanoseconds

Explanation: The Y channels interrogation pulse pairs are spaced by 36 microseconds. However, the Y channel reply pulse pairs are spaced by 30 microseconds.

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