DGCA Air Navigation: Radar Theory Questions
167 exam-style Radar Theory questions for the DGCA Air Navigationpaper (CPL & ATPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
- Q1
A modern Radio Altimeter uses the frequency band:
- AVHF 30 - 300 Mhz
- BSHF 3000 Mhz - 30 Ghz
- CUHF 300 Mhz - 3 Ghz
- DHF 3 Mhz - 30 Mhz
Show answer
Correct answer: B. SHF 3000 Mhz - 30 Ghz
This Explanation is Coming Soon
- Q2
A Primary radar operates on the principle of:
- A pulse technique
- Btransponder interrogation
- C phase comparison
- D continuous wave transmission
Show answer
Correct answer: A. pulse technique
Primary radar works on the pulse technique, transmitting short pulses and timing the energy reflected from a passive target.
- Q3
The main factor which determines the minimum range that can be measured by a pulsed radar is pulse:
- A length
- B amplitude
- C repetition rate
- D frequency
Show answer
Correct answer: A. length
The minimum range a pulsed radar can measure is set by the pulse length, since the receiver is blanked while the pulse is still being transmitted.
- Q4
Ignoring pulse length, the maximum pulse repetition frequency (PRF) that can be used by a primary radar facility to detect targets unambiguously to a range of 200 NM is:(pps = pulses per second)
- A 405 pps
- B 782 pps
- C 308 pps
- D375 pps
Show answer
Correct answer: A. 405 pps
For unambiguous detection to 200 NM the echo must return before the next pulse; the round-trip time of about 2472 microseconds limits the pulse repetition frequency to roughly 405 pulses per second.
- Q5
The maximum range of primary radar depends on :
- Apulse recurrence frequency
- Bwave length
- Cfrequency
- Dpulse length
Show answer
Correct answer: A. pulse recurrence frequency
The maximum unambiguous range of a primary radar is set by its pulse recurrence frequency, which fixes the listening time available between transmitted pulses.
- Q6
For any given circumstances, in order to double the effective range of a primary radar the power output must be increased by a factor of:
- A 16
- B 2
- C4
- D8
Show answer
Correct answer: A. 16
Because received power falls off with the fourth power of range, radar range depends on the fourth root of transmitted power, so doubling the range requires increasing the power by a factor of 2⁴, that is sixteen times.
- Q7
The prime factor in determining the maximum unambiguous range of a primary radar is the:
- A pulse recurrence rate
- B power output
- C size of parabolic receiver aerial
- Dheight of the transmitter above the ground
Show answer
Correct answer: A. pulse recurrence rate
Maximum unambiguous range is set by the pulse recurrence rate, since the interval between transmitted pulses must be long enough for an echo from the most distant target to return before the next pulse is sent, otherwise ranges become ambiguous.
- Q8
A Radio Altimeter is:
- Aground based and measures true altitude
- Bground based and measures true height
- Caircraft based and measures true altitude
- Daircraft based and measures true height
Show answer
Correct answer: D. aircraft based and measures true height
This Explanation is Coming Soon
- Q9
The advantage of the use of slotted antennas in modern radar technology is to:
- Avirtually eliminate lateral lobes and as a consequence concentrate more energy in the main beam
- B simultaneously transmit weather and mapping beams
- C have a wide beam and as a consequence better target detection
- D eliminate the need for azimuth slaving
Show answer
Correct answer: A. virtually eliminate lateral lobes and as a consequence concentrate more energy in the main beam
Slotted planar antennas suppress the unwanted side lobes and concentrate the radiated energy into the main beam, improving resolution and reducing spurious returns.
- Q10
Which of the following types of radar systems are most suited for short range operation?
- A primary continuous wave
- B centimetric pulse
- Cmillimetric pulse
- Dsecondary continuous wave
Show answer
Correct answer: A. primary continuous wave
Continuous-wave primary radar suits short-range work because it has no minimum-range limitation created by pulse timing, making it well adapted to close measurement such as radio altimetry.
- Q11
In which frequency band do most airborne weather, and ground based ATC, radar systems operate?
- ASHF
- BUHF
- CEHF
- D VHF
Show answer
Correct answer: A. SHF
Most airborne weather and ground ATC radars operate in the SHF (Super High Frequency) band, whose short wavelengths give the narrow beams and good resolution these radars require.
- Q12
Which of the following equipments uses primary radar principles?
- A Airborne weather radar (AWR)
- B Secondary Surveillance Radar (SSR)
- C Distance Measuring Equipment (DME)
- D Global Positioning System (GPS)
Show answer
Correct answer: A. Airborne weather radar (AWR)
Airborne weather radar works on primary radar principles, transmitting a pulse and displaying the energy reflected back from targets, unlike SSR, DME or GPS which depend on transponder replies or one-way signals.
155 more Radar Theory questions in the full bank
Create a free account to practise every Radar Theory question with instant scoring, chapter tests, previous DGCA papers and full-length mock exams.
Start practising free