General G4C: Interference, grounding and bonding
These are the 12 official questions in group G4C 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.
- G4C01Question 1
Which of the following might be useful in reducing RF interference to audio frequency circuits?
- ABypass inductor
- BBypass capacitor Correct
- CForward-biased diode
- DReverse-biased diode
Why: A bypass capacitor shunts RF away from audio circuits.
- G4C02Question 2
Which of the following could be a cause of interference covering a wide range of frequencies?
- ANot using a balun or line isolator to feed balanced antennas
- BLack of rectification of the transmitter’s signal in power conductors
- CArcing at a poor electrical connection Correct
- DUsing a balun to feed an unbalanced antenna
Why: Arcing at a poor connection makes broadband interference.
- G4C03Question 3
What sound is heard from an audio device experiencing RF interference from a single sideband phone transmitter?
- AA steady hum whenever the transmitter is on the air
- BOn-and-off humming or clicking
- CDistorted speech Correct
- DClearly audible speech
Why: RF from an SSB transmitter sounds like distorted speech in audio gear.
- G4C04Question 4
What sound is heard from an audio device experiencing RF interference from a CW transmitter?
- AOn-and-off humming or clicking Correct
- BA CW signal at a nearly pure audio frequency
- CA chirpy CW signal
- DSeverely distorted audio
Why: RF from a CW transmitter sounds like on-and-off humming or clicking.
- G4C05Question 5
What is a possible cause of high voltages that produce RF burns?
- AFlat braid rather than round wire has been used for the ground wire
- BInsulated wire has been used for the ground wire
- CThe ground rod is resonant
- DThe ground wire has high impedance on that frequency Correct
Why: A ground wire with high impedance at the operating frequency can let high RF voltage build up.
- G4C06Question 6
What is a possible effect of a resonant ground connection?
- AOverheating of ground straps
- BCorrosion of the ground rod
- CHigh RF voltages on the enclosures of station equipment Correct
- DA ground loop
Why: A resonant ground lead can put high RF voltage on equipment cases.
- G4C07Question 7
Why should soldered joints not be used in lightning protection ground connections?
- AA soldered joint will likely be destroyed by the heat of a lightning strike Correct
- BSolder flux will prevent a low conductivity connection
- CSolder has too high a dielectric constant to provide adequate lightning protection
- DAll these choices are correct
Why: A lightning strike's heat would likely destroy a soldered joint.
- G4C08Question 8
Which of the following would reduce RF interference caused by common-mode current on an audio cable?
- APlace a ferrite choke on the cable Correct
- BConnect the center conductor to the shield of all cables to short circuit the RFI signal
- CGround the center conductor of the audio cable causing the interference
- DAdd an additional insulating jacket to the cable
Why: A ferrite choke on the cable reduces common-mode current.
- G4C09Question 9
How can the effects of ground loops be minimized?
- AConnect all ground conductors in series
- BConnect the AC neutral conductor to the ground wire
- CAvoid using lock washers and star washers when making ground connections
- DBond equipment enclosures together Correct
Why: Bonding equipment enclosures together minimizes ground loops.
- G4C10Question 10
What could be a symptom caused by a ground loop in your station’s audio connections?
- AYou receive reports of “hum” on your station’s transmitted signal Correct
- BThe SWR reading for one or more antennas is suddenly very high
- CAn item of station equipment starts to draw excessive amounts of current
- DYou receive reports of harmonic interference from your station
Why: A ground loop in the audio wiring can put hum on your transmitted signal.
- G4C11Question 11
What technique helps to minimize RF “hot spots” in an amateur station?
- ABuilding all equipment in a metal enclosure
- BUsing surge suppressor power outlets
- CBonding all equipment enclosures together Correct
- DPlacing low-pass filters on all feed lines
Why: Bonding all enclosures together minimizes RF hot spots.
- G4C12Question 12
Why must all metal enclosures of station equipment be grounded?
- AIt prevents a blown fuse in the event of an internal short circuit
- BIt prevents signal overload
- CIt ensures that the neutral wire is grounded
- DIt ensures that hazardous voltages cannot appear on the chassis Correct
Why: Grounding enclosures keeps hazardous voltages off the chassis.