General G4A: Receiver and transmitter controls
These are the 13 official questions in group G4A 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.
- G4A01Question 1
What is the purpose of the notch filter found on many HF transceivers?
- ATo restrict the transmitter voice bandwidth
- BTo reduce interference from carriers in the receiver passband Correct
- CTo eliminate receiver interference from impulse noise sources
- DTo remove interfering splatter generated by signals on adjacent frequencies
Why: A notch filter removes interfering carriers from the receiver passband.
- G4A02Question 2
What is the benefit of using the opposite or “reverse” sideband when receiving CW?
- AInterference from impulse noise will be eliminated
- BMore stations can be accommodated within a given signal passband
- CIt may be possible to reduce or eliminate interference from other signals Correct
- DAccidental out-of-band operation can be prevented
Why: Receiving CW on the opposite sideband can move interference out of the way.
- G4A03Question 3
How does a noise blanker work?
- ABy temporarily increasing received bandwidth
- BBy redirecting noise pulses into a filter capacitor
- CBy reducing receiver gain during a noise pulse Correct
- DBy clipping noise peaks
Why: A noise blanker cuts receiver gain during each noise pulse.
- G4A04Question 4
What is the effect on plate current of the correct setting of a vacuum-tube RF power amplifier’s TUNE control?
- AA pronounced peak
- BA pronounced dip Correct
- CNo change will be observed
- DA slow, rhythmic oscillation
Why: Correct TUNE on a tube amplifier shows a pronounced dip in plate current.
- G4A05Question 5
Why is automatic level control (ALC) used with an RF power amplifier?
- ATo balance the transmitter audio frequency response
- BTo reduce harmonic radiation
- CTo prevent excessive drive Correct
- DTo increase overall efficiency
Why: ALC keeps the amplifier from being overdriven.
- G4A06Question 6
What is the purpose of an antenna tuner?
- AReduce the SWR in the feed line to the antenna
- BReduce the power dissipation in the feedline to the antenna
- CIncrease power transfer from the transmitter to the feed line Correct
- DAll these choices are correct
Why: An antenna tuner increases power transfer from the transmitter to the feed line.
- G4A07Question 7
What happens as a receiver’s noise reduction control level is increased?
- AReceived signals may become distorted Correct
- BReceived frequency may become unstable
- CCW signals may become severely attenuated
- DReceived frequency may shift several kHz
Why: Too much noise reduction can distort received signals.
- G4A08Question 8
What is the correct adjustment for the LOAD or COUPLING control of a vacuum tube RF power amplifier?
- AMinimum SWR on the antenna
- BMinimum plate current without exceeding maximum allowable grid current
- CHighest plate voltage while minimizing grid current
- DDesired power output without exceeding maximum allowable plate current Correct
Why: Adjust LOAD for the desired power without exceeding the maximum plate current.
- G4A09Question 9
What is the purpose of delaying RF output after activating a transmitter’s keying line to an external amplifier?
- ATo prevent key clicks on CW
- BTo prevent transient overmodulation
- CTo allow time for the amplifier to switch the antenna between the transceiver and the amplifier output Correct
- DTo allow time for the amplifier power supply to reach operating level
Why: The delay gives the amplifier time to switch its antenna relay before RF arrives.
- G4A10Question 10
What is the function of an electronic keyer?
- AAutomatic transmit/receive switching
- BAutomatic generation of dots and dashes for CW operation Correct
- CTo allow time for switching the antenna from the receiver to the transmitter
- DComputer interface for PSK and RTTY operation
Why: An electronic keyer automatically generates dots and dashes.
- G4A11Question 11
Why should the ALC system be inactive when transmitting AFSK data signals?
- AALC will invert the modulation of the AFSK mode
- BThe ALC action distorts the signal Correct
- CWhen using digital modes, too much ALC activity can cause the transmitter to overheat
- DAll these choices are correct
Why: ALC action distorts AFSK data signals, so keep it inactive.
- G4A12Question 12
Which of the following is a common use of the dual-VFO feature on a transceiver?
- ATo allow transmitting on two frequencies at once
- BTo permit full duplex operation -- that is, transmitting and receiving at the same time
- CTo transmit on one frequency and listen on another Correct
- DTo improve frequency accuracy by allowing variable frequency output (VFO) operation
Why: Dual VFOs let you transmit on one frequency and listen on another.
- G4A13Question 13
What is the purpose of using a receive attenuator?
- ATo prevent receiver overload from strong incoming signals Correct
- BTo reduce the transmitter power when driving a linear amplifier
- CTo reduce power consumption when operating from batteries
- DTo reduce excessive audio level on strong signals
Why: An attenuator prevents receiver overload from strong signals.