FCC ELEMENT 3 TEST QUESTIONS
WITH CORRECT DETAILED
ANSWERS
What is the name of the type of modulation in which the modulating signal varies the
duration of the transmitted pulse?
A. Amplitude modulation.
B. Frequency modulation.
C. Pulse-height modulation.
D. Pulse-width modulation. - Answer-D. Pulse-width modulation.
Which of the following best describes a pulse modulation system?
A. The peak transmitter power is normally much greater than the average power.
B. Pulse modulation is sometimes used in SSB voice transmitters.
C. The average power is normally only slightly below the peak power.
D. The peak power is normally twice as high as the average power. - Answer-A. The
peak transmitter power is normally much greater than the average power.
In a pulse-position modulation system, what parameter does the modulating signal
vary?
A. The number of pulses per second.
B. The time at which each pulse occurs.
C. Both the frequency and amplitude of the pulses.
D. The duration of the pulses. - Answer-B. The time at which each pulse occurs.
What is one way that voice is transmitted in a pulse-width modulation system?
A. A standard pulse is varied in amplitude by an amount depending on the voice
waveform at that instant.
B. The position of a standard pulse is varied by an amount depending on the voice
waveform at that instant.
C. A standard pulse is varied in duration by an amount depending on the voice
waveform at that instant.
D. The number of standard pulses per second varies depending on the voice waveform
at that instant. - Answer-C. A standard pulse is varied in duration by an amount
depending on the voice waveform at that instant.
When a lead-acid storage battery is being charged, a harmful effect to humans is:
A. Internal plate sulfation may occur under constant charging.
B. Emission of oxygen.
C. Emission of chlorine gas.
D. Emission of hydrogen gas. - Answer-D. Emission of hydrogen gas.
,A battery with a terminal voltage of 12.5 volts is to be trickle-charged at a 0.5 A rate.
What resistance should be connected in series with the battery to charge it from a 110-
V DC line?
A. 95 ohms.
B. 300 ohms.
C. 195 ohms.
D. None of these. - Answer-C. 195 ohms.
What capacity in amperes does a storage battery need to be in order to operate a 50
watt transmitter for 6 hours? Assume a continuous transmitter load of 70% of the key-
locked demand of 40 A, and an emergency light load of 1.5 A.
A. 100 ampere-hours.
B. 177 ampere-hours.
C. 249 ampere-hours.
D. None of these. - Answer-B. 177 ampere-hours.
What is the total voltage when 12 Nickel-Cadmium batteries are connected in series?
A. 12 volts.
B. 12.6 volts.
C. 15 volts.
D. 72 volts. - Answer-C. 15 volts.
The average fully-charged voltage of a lead-acid storage cell is:
A. 1 volt.
B. 1.2 volts.
C. 1.56 volts.
D. 2.06 volts. - Answer-D. 2.06 volts.
A nickel-cadmium cell has an operating voltage of about:
A. 1.25 volts.
B. 1.4 volts.
C. 1.5 volts.
D. 2.1 volts. - Answer-A. 1.25 volts.
When an emergency transmitter uses 325 watts and a receiver uses 50 watts, how
many hours can a 12.6 volt, 55 ampere-hour battery supply full power to both units?
A. 1.8 hours.
B. 6 hours.
C. 3 hours.
D. 1.2 hours. - Answer-A. 1.8 hours.
What current will flow in a 6 volt storage battery with an internal resistance of 0.01
ohms, when a 3-watt, 6-volt lamp is connected?
A. 0.4885 amps.
B. 0.4995 amps.
C. 0.5566 amps.
,D. 0.5795 amps. - Answer-B. 0.4995 amps.
A ship RADAR unit uses 315 watts and a radio uses 50 watts. If the equipment is
connected to a 50 ampere-hour battery rated at 12.6 volts, how long will the battery
last?
A. 1 hour 43 minutes.
B. 28.97 hours.
C. 29 minutes.
D. 10 hours, 50 minutes. - Answer-A. 1 hour 43 minutes.
If a marine radiotelephone receiver uses 75 watts of power and a transmitter uses 325
watts, how long can they both operate before discharging a 50 ampere-hour 12 volt
battery?
A. 40 minutes.
B. 1 hour.
C. 1 1/2 hours.
D. 6 hours. - Answer-C. 1 1/2 hours.
A 6 volt battery with 1.2 ohms internal resistance is connected across two light bulbs in
parallel whose resistance is 12 ohms each. What is the current flow?
A. 0.57 amps.
B. 0.83 amps.
C. 1.0 amps.
D. 6.0 amps. - Answer-B. 0.83 amps.
A 12.6 volt, 8 ampere-hour battery is supplying power to a receiver that uses 50 watts
and a RADAR system that uses 300 watts. How long will the battery last?
A. 100.8 hours.
B. 27.7 hours.
C. 1 hour.
D. 17 minutes or 0.3 hours. - Answer-D. 17 minutes or 0.3 hours.
What occurs if the load is removed from an operating series DC motor?
A. It will stop running.
B. Speed will increase slightly.
C. No change occurs.
D. It will accelerate until it falls apart. - Answer-D. It will accelerate until it falls apart.
If a shunt motor running with a load has its shunt field opened, how would this affect the
speed of the motor?
A. It will slow down.
B. It will stop suddenly.
C. It will speed up.
D. It will be unaffected. - Answer-C. It will speed up.
, The expression "voltage regulation" as it applies to a shunt-wound DC generator
operating at a constant frequency refers to:
A. Voltage fluctuations from load to no-load.
B. Voltage output efficiency.
C. Voltage in the secondary compared to the primary.
D. Rotor winding voltage ratio - Answer-A. Voltage fluctuations from load to no-load.
What is the line current of a 7 horsepower motor operating on 120 volts at full load, a
power factor of 0.8, and 95% efficient?
A. 4.72 amps.
B. 13.03 amps.
C. 56 amps.
D. 57.2 amps. - Answer-D. 57.2 amps.
A 3 horsepower, 100 V DC motor is 85% efficient when developing its rated output.
What is the current?
A. 8.545 amps.
B. 20.345 amps.
C. 26.300 amps.
D. 25.000 amps. - Answer-C. 26.300 amps.
The output of a separately-excited AC generator running at a constant speed can be
controlled by: A. The armature.
B. The amount of field current.
C. The brushes.
D. The exciter. - Answer-B. The amount of field current.
Which of the following could cause a high standing wave ratio on a transmission line?
A. Excessive modulation.
B. An increase in output power.
C. A detuned antenna coupler.
D. Low power from the transmitter. - Answer-C. A detuned antenna coupler.
Why is the value of the radiation resistance of an antenna important?
A. Knowing the radiation resistance makes it possible to match impedances for
maximum power transfer.
B. Knowing the radiation resistance makes it possible to measure the near-field
radiation density from
transmitting antenna.
C. The value of the radiation resistance represents the front-to-side ratio of the antenna.
\D. The value of the radiation resistance represents the front-to-back ratio of the
antenna. - Answer-A. Knowing the radiation resistance makes it possible to match
impedances for maximum power transfer.
A radio frequency device that allows RF energy to pass through in one direction with
very little loss but absorbs RF power in the opposite direction is a:
WITH CORRECT DETAILED
ANSWERS
What is the name of the type of modulation in which the modulating signal varies the
duration of the transmitted pulse?
A. Amplitude modulation.
B. Frequency modulation.
C. Pulse-height modulation.
D. Pulse-width modulation. - Answer-D. Pulse-width modulation.
Which of the following best describes a pulse modulation system?
A. The peak transmitter power is normally much greater than the average power.
B. Pulse modulation is sometimes used in SSB voice transmitters.
C. The average power is normally only slightly below the peak power.
D. The peak power is normally twice as high as the average power. - Answer-A. The
peak transmitter power is normally much greater than the average power.
In a pulse-position modulation system, what parameter does the modulating signal
vary?
A. The number of pulses per second.
B. The time at which each pulse occurs.
C. Both the frequency and amplitude of the pulses.
D. The duration of the pulses. - Answer-B. The time at which each pulse occurs.
What is one way that voice is transmitted in a pulse-width modulation system?
A. A standard pulse is varied in amplitude by an amount depending on the voice
waveform at that instant.
B. The position of a standard pulse is varied by an amount depending on the voice
waveform at that instant.
C. A standard pulse is varied in duration by an amount depending on the voice
waveform at that instant.
D. The number of standard pulses per second varies depending on the voice waveform
at that instant. - Answer-C. A standard pulse is varied in duration by an amount
depending on the voice waveform at that instant.
When a lead-acid storage battery is being charged, a harmful effect to humans is:
A. Internal plate sulfation may occur under constant charging.
B. Emission of oxygen.
C. Emission of chlorine gas.
D. Emission of hydrogen gas. - Answer-D. Emission of hydrogen gas.
,A battery with a terminal voltage of 12.5 volts is to be trickle-charged at a 0.5 A rate.
What resistance should be connected in series with the battery to charge it from a 110-
V DC line?
A. 95 ohms.
B. 300 ohms.
C. 195 ohms.
D. None of these. - Answer-C. 195 ohms.
What capacity in amperes does a storage battery need to be in order to operate a 50
watt transmitter for 6 hours? Assume a continuous transmitter load of 70% of the key-
locked demand of 40 A, and an emergency light load of 1.5 A.
A. 100 ampere-hours.
B. 177 ampere-hours.
C. 249 ampere-hours.
D. None of these. - Answer-B. 177 ampere-hours.
What is the total voltage when 12 Nickel-Cadmium batteries are connected in series?
A. 12 volts.
B. 12.6 volts.
C. 15 volts.
D. 72 volts. - Answer-C. 15 volts.
The average fully-charged voltage of a lead-acid storage cell is:
A. 1 volt.
B. 1.2 volts.
C. 1.56 volts.
D. 2.06 volts. - Answer-D. 2.06 volts.
A nickel-cadmium cell has an operating voltage of about:
A. 1.25 volts.
B. 1.4 volts.
C. 1.5 volts.
D. 2.1 volts. - Answer-A. 1.25 volts.
When an emergency transmitter uses 325 watts and a receiver uses 50 watts, how
many hours can a 12.6 volt, 55 ampere-hour battery supply full power to both units?
A. 1.8 hours.
B. 6 hours.
C. 3 hours.
D. 1.2 hours. - Answer-A. 1.8 hours.
What current will flow in a 6 volt storage battery with an internal resistance of 0.01
ohms, when a 3-watt, 6-volt lamp is connected?
A. 0.4885 amps.
B. 0.4995 amps.
C. 0.5566 amps.
,D. 0.5795 amps. - Answer-B. 0.4995 amps.
A ship RADAR unit uses 315 watts and a radio uses 50 watts. If the equipment is
connected to a 50 ampere-hour battery rated at 12.6 volts, how long will the battery
last?
A. 1 hour 43 minutes.
B. 28.97 hours.
C. 29 minutes.
D. 10 hours, 50 minutes. - Answer-A. 1 hour 43 minutes.
If a marine radiotelephone receiver uses 75 watts of power and a transmitter uses 325
watts, how long can they both operate before discharging a 50 ampere-hour 12 volt
battery?
A. 40 minutes.
B. 1 hour.
C. 1 1/2 hours.
D. 6 hours. - Answer-C. 1 1/2 hours.
A 6 volt battery with 1.2 ohms internal resistance is connected across two light bulbs in
parallel whose resistance is 12 ohms each. What is the current flow?
A. 0.57 amps.
B. 0.83 amps.
C. 1.0 amps.
D. 6.0 amps. - Answer-B. 0.83 amps.
A 12.6 volt, 8 ampere-hour battery is supplying power to a receiver that uses 50 watts
and a RADAR system that uses 300 watts. How long will the battery last?
A. 100.8 hours.
B. 27.7 hours.
C. 1 hour.
D. 17 minutes or 0.3 hours. - Answer-D. 17 minutes or 0.3 hours.
What occurs if the load is removed from an operating series DC motor?
A. It will stop running.
B. Speed will increase slightly.
C. No change occurs.
D. It will accelerate until it falls apart. - Answer-D. It will accelerate until it falls apart.
If a shunt motor running with a load has its shunt field opened, how would this affect the
speed of the motor?
A. It will slow down.
B. It will stop suddenly.
C. It will speed up.
D. It will be unaffected. - Answer-C. It will speed up.
, The expression "voltage regulation" as it applies to a shunt-wound DC generator
operating at a constant frequency refers to:
A. Voltage fluctuations from load to no-load.
B. Voltage output efficiency.
C. Voltage in the secondary compared to the primary.
D. Rotor winding voltage ratio - Answer-A. Voltage fluctuations from load to no-load.
What is the line current of a 7 horsepower motor operating on 120 volts at full load, a
power factor of 0.8, and 95% efficient?
A. 4.72 amps.
B. 13.03 amps.
C. 56 amps.
D. 57.2 amps. - Answer-D. 57.2 amps.
A 3 horsepower, 100 V DC motor is 85% efficient when developing its rated output.
What is the current?
A. 8.545 amps.
B. 20.345 amps.
C. 26.300 amps.
D. 25.000 amps. - Answer-C. 26.300 amps.
The output of a separately-excited AC generator running at a constant speed can be
controlled by: A. The armature.
B. The amount of field current.
C. The brushes.
D. The exciter. - Answer-B. The amount of field current.
Which of the following could cause a high standing wave ratio on a transmission line?
A. Excessive modulation.
B. An increase in output power.
C. A detuned antenna coupler.
D. Low power from the transmitter. - Answer-C. A detuned antenna coupler.
Why is the value of the radiation resistance of an antenna important?
A. Knowing the radiation resistance makes it possible to match impedances for
maximum power transfer.
B. Knowing the radiation resistance makes it possible to measure the near-field
radiation density from
transmitting antenna.
C. The value of the radiation resistance represents the front-to-side ratio of the antenna.
\D. The value of the radiation resistance represents the front-to-back ratio of the
antenna. - Answer-A. Knowing the radiation resistance makes it possible to match
impedances for maximum power transfer.
A radio frequency device that allows RF energy to pass through in one direction with
very little loss but absorbs RF power in the opposite direction is a:
