General G7B: Amplifiers, oscillators and logic
These are the 11 official questions in group G7B of the 2023–2027 General question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- G7B01Question 1
What is the purpose of neutralizing an amplifier?
- ATo limit the modulation index
- BTo eliminate self-oscillations Correct
- CTo cut off the final amplifier during standby periods
- DTo keep the carrier on frequency
Why: Neutralizing an amplifier eliminates self-oscillation.
- G7B02Question 2
Which of these classes of amplifiers has the highest efficiency?
- AClass A
- BClass B
- CClass AB
- DClass C Correct
Why: Class C is the most efficient amplifier class.
- G7B03Question 3
Which of the following describes the function of a two-input AND gate?
- AOutput is high when either or both inputs are low
- BOutput is high only when both inputs are high Correct
- COutput is low when either or both inputs are high
- DOutput is low only when both inputs are high
Why: A two-input AND gate's output is high only when both inputs are high.
- G7B04Question 4
In a Class A amplifier, what percentage of the time does the amplifying device conduct?
- A100% Correct
- BMore than 50% but less than 100%
- C50%
- DLess than 50%
Why: A Class A device conducts 100% of the time.
- G7B05Question 5
How many states does a 3-bit binary counter have?
- A3
- B6
- C8 Correct
- D16
Why: 3 bits give 2³ = 8 states.
- G7B06Question 6
What is a shift register?
- AA clocked array of circuits that passes data in steps along the array Correct
- BAn array of operational amplifiers used for tri-state arithmetic operations
- CA digital mixer
- DAn analog mixer
Why: A shift register is a clocked array that passes data along in steps.
- G7B07Question 7
Which of the following are basic components of a sine wave oscillator?
- AAn amplifier and a divider
- BA frequency multiplier and a mixer
- CA circulator and a filter operating in a feed-forward loop
- DA filter and an amplifier operating in a feedback loop Correct
Why: A sine wave oscillator is a filter and an amplifier in a feedback loop.
- G7B08Question 8
How is the efficiency of an RF power amplifier determined?
- ADivide the DC input power by the DC output power
- BDivide the RF output power by the DC input power Correct
- CMultiply the RF input power by the reciprocal of the RF output power
- DAdd the RF input power to the DC output power
Why: Efficiency = RF output power ÷ DC input power.
- G7B09Question 9
What determines the frequency of an LC oscillator?
- AThe number of stages in the counter
- BThe number of stages in the divider
- CThe inductance and capacitance in the tank circuit Correct
- DThe time delay of the lag circuit
Why: The tank circuit's inductance and capacitance set an LC oscillator's frequency.
- G7B10Question 10
Which of the following describes a linear amplifier?
- AAny RF power amplifier used in conjunction with an amateur transceiver
- BAn amplifier in which the output preserves the input waveform Correct
- CA Class C high efficiency amplifier
- DAn amplifier used as a frequency multiplier
Why: A linear amplifier's output preserves the input waveform.
- G7B11Question 11
For which of the following modes is a Class C power stage appropriate for amplifying a modulated signal?
- ASSB
- BFM Correct
- CAM
- DAll these choices are correct
Why: FM has constant amplitude, so a Class C stage works for it.