Deep Dive: T7B04
The correct answer is Ferrite choke. A ferrite choke (also called a ferrite core or ferrite bead) can cure distorted audio caused by RF current on the shield of a microphone cable. RF current flowing on the cable shield can couple into the audio circuits, causing distortion, feedback, and interference. A ferrite choke placed around the microphone cable creates impedance to RF currents while allowing audio frequencies to pass, blocking the unwanted RF. For amateur radio operators, ferrite chokes are simple, effective solutions for RF feedback problems in microphone cables, speaker cables, and other audio connections. They're inexpensive and easy to install.
Why Other Answers Are Wrong
Option A (Band-pass filter): Incorrect. A band-pass filter passes a specific frequency range. It doesn't block RF on cable shields - it filters frequencies in signal paths. Option B (Low-pass filter): Incorrect. A low-pass filter passes low frequencies and blocks high frequencies, but it's for signal paths, not for blocking RF on cable shields. Option C (Preamplifier): Incorrect. A preamplifier amplifies signals, which would make the RF interference worse, not better. It doesn't block RF on cable shields.
Exam Tip
Ferrite choke = blocks RF on cable shields. Think 'F'errite 'C'hoke = 'F'ilters 'C'able RF. It creates impedance to RF while passing audio. Filters are for signal paths, not cable shields.
Memory Aid
Ferrite choke = Filters RF on cables. Think 'F'errite 'C'hoke = 'F'ilters 'C'able RF. Blocks RF on shields while passing audio signals.
Real-World Example
When transmitting, RF from your antenna couples onto your microphone cable shield, causing distorted audio and feedback. Wrapping the cable through a ferrite choke (or placing ferrite beads on the cable) creates impedance to the RF current, blocking it from entering your audio circuits. The audio signals pass through normally, but the RF interference is suppressed. This is a common and effective solution for RF feedback problems.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7B
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7B topic.