All 30 FCC GROL questions for 3O RADAR with the correct answers marked, from the official current FCC question pool. Test yourself with the free practice exam.
3-90O1
What is the normal range of pulse repetition rates?
A. 2,000 to 4,000 pps.
B. 1,000 to 3,000 pps.
C. 500 to 1,000 pps.
D. 500 to 2,000 pps. ✓
3-90O2
The RADAR range in nautical miles to an object can be found by measuring the elapsed time during a RADAR pulse and dividing this quantity by:
A. 0.87 seconds.
B. 1.15 µs.
C. 12.346 µs. ✓
D. 1.073 µs.
3-90O3
What is the normal range of pulse widths?
A. .05 s to 0.1 s.
B. .05 s to 1.0 s. ✓
C. 1.0 s to 3.5 s.
D. 2.5 s to 5.0 s.
3-90O4
Shipboard RADAR is most commonly operated in what band?
A. VHF.
B. UHF.
C. SHF. ✓
D. EHF.
3-90O5
The pulse repetition rate (prr) of a RADAR refers to the:
A. Reciprocal of the duty cycle.
B. Pulse rate of the local oscillator.
C. Pulse rate of the klystron.
D. Pulse rate of the magnetron. ✓
3-90O6
If the elapsed time for a RADAR echo is 62 microseconds, what is the distance in nautical miles to the object?
A. 5 nautical miles. ✓
B. 87 nautical miles.
C. 37 nautical miles.
D. 11.5 nautical miles.
3-91O1
The ATR box:
A. Prevents the received signal from entering the transmitter. ✓
B. Protects the receiver from strong RADAR signals.
C. Turns off the receiver when the transmitter is on.
D. All of the above.
3-91O2
What is the purpose or function of the RADAR duplexer/circulator? It is a/an:
A. Coupling device that is used in the transition from a rectangular waveguide to a circular waveguide.
B. Electronic switch that allows the use of one antenna for both transmission and reception. ✓
C. Modified length of waveguide that is used to sample a portion of the transmitted energy for testing purposes.
D. Dual section coupling device that allows the use of a magnetron as a transmitter.
3-91O3
What device can be used to determine the performance of a RADAR system at sea?
A. Echo box. ✓
B. Klystron.
C. Circulator.
D. Digital signal processor.
3-91O4
What is the purpose of a synchro transmitter and receiver?
A. Synchronizes the transmitted and received pulse trains.
B. Prevents the receiver from operating during the period of the transmitted pulse.
C. Transmits the angular position of the antenna to the indicator unit. ✓
D. Keeps the speed of the motor generator constant.
3-91O5
Digital signal processing (DSP) of RADAR signals (compared with analog) causes:
A. Improved display graphics.
B. Improved weak signal or target enhancement. ✓
C. Less interference with SONAR systems.
D. Less interference with other radio communications equipment.
3-91O6
The component or circuit providing the transmitter output power for a RADAR system is the:
A. Thyratron.
B. SCR.
C. Klystron.
D. Magnetron. ✓
3-92O1
When a RADAR is being operated on the 48 mile range setting, what is the most appropriate pulse width (PW) and pulse repetition rate (pps)?
A. 1.0 s PW and 2,000 pps.
B. 0.05 s PW and 2,000 pps.
C. 2.5 s PW and 2,500 pps.
D. 1.0 s PW and 500 pps. ✓
3-92O2
When a RADAR is being operated on the 6 mile range setting what is the most appropriate pulse width and pulse repetition rate?
A. 1.0 s PW and 500 pps.
B. 2.0 s PW and 3,000 pps.
C. 0.25 s PW and 1,000 pps. ✓
D. 0.01 s PW and 500 pps.
3-92O3
We are looking at a target 25 miles away. When a RADAR is being operated on the 25 mile range setting what is the most appropriate pulse width and pulse repetition rate?
A. 1.0 s PW and 500 pps. ✓
B. 0.25 s PW and 1,000 pps.
C. 0.01 s PW and 500 pps.
D. 0.05 s PW and 2,000 pps.
3-92O4
What pulse width and repetition rate should you use at long ranges?
A. Narrow pulse width and slow repetition rate.
B. Narrow pulse width and fast repetition rate.
C. Wide pulse width and fast repetition rate.
D. Wide pulse width and slow repetition rate. ✓
3-92O5
What pulse width and repetition rate should you use at short ranges?
A. Wide pulse width and fast repetition rate.
B. Narrow pulse width and slow repetition rate.
C. Narrow pulse width and fast repetition rates. ✓
D. Wide pulse width and slow repetition rates.
3-92O6
When a RADAR is being operated on the 1.5 mile range setting, what is the most appropriate pulse width and pulse repetition rate?
A. 0.25 s PW and 1,000 pps.
B. 0.05 s PW and 2,000 pps. ✓
C. 1.0 s PW and 500 pps.
D. 2.5 s PW and 2,500 pps.
3-93O1
How does the gain of a parabolic dish antenna change when the operating frequency is doubled?
A. Gain does not change.
B. Gain is multiplied by 0.707.
C. Gain increases 6 dB. ✓
D. Gain increases 3 dB.
3-93O2
What type of antenna or pickup device is used to extract the RADAR signal from the wave guide?
A. J-hook. ✓
B. K-hook.
C. Folded dipole.
D. Circulator.
3-93O3
What happens to the beamwidth of an antenna as the gain is increased? The beamwidth:
A. Increases geometrically as the gain is increased.
B. Increases arithmetically as the gain is increased.
C. Is essentially unaffected by the gain of the antenna.
D. Decreases as the gain is increased. ✓
3-93O4
A common shipboard RADAR antenna is the:
A. Slotted array. ✓
B. Dipole.
C. Stacked Yagi.
D. Vertical Marconi.
3-93O5
Conductance takes place in a waveguide:
A. By interelectron delay.
B. Through electrostatic field reluctance.
C. In the same manner as a transmission line.
D. Through electromagnetic and electrostatic fields in the walls of the waveguide. ✓
3-93O6
To couple energy into and out of a waveguide use:
A. Wide copper sheeting.
B. A thin piece of wire as an antenna. ✓
C. An LC circuit.
D. Capacitive coupling.
3-94O1
The permanent magnetic field that surrounds a traveling-wave tube (TWT) is intended to:
A. Provide a means of coupling.
B. Prevent the electron beam from spreading. ✓
C. Prevent oscillations.
D. Prevent spurious oscillations.
3-94O2
Prior to testing any RADAR system, the operator should first:
A. Check the system grounds.
B. Assure the display unit is operating normally.
C. Inform the airport control tower or ship’s master.
D. Assure no personnel are in front of the antenna. ✓
3-94O3
In the term “ARPA RADAR,” ARPA is the acronym for which of the following?
A. Automatic RADAR Plotting Aid. ✓
B. Automatic RADAR Positioning Angle.
C. American RADAR Programmers Association.
D. Authorized RADAR Programmer and Administrator.
3-94O4
Which of the following is NOT a precaution that should be taken to ensure the magnetron is not weakened:
A. Keep metal tools away from the magnet.
B. Do not subject it to excessive heat.
C. Keep the TR properly tuned. ✓
D. Do not subject it to shocks and blows.
3-94O5
Exposure to microwave energy from RADAR or other electronics devices is limited by U.S. Health Department regulations to _______ mW/centimeter.
A. 0.005
B. 5.0 ✓
C. 0.05
D. 0.5
3-94O6
RADAR collision avoidance systems utilize inputs from each of the following except your ship’s:
A. Gyrocompass.
B. Navigation position receiver.
C. Anemometer. ✓
D. Speed indicator.