Which of the following could you use to cure distorted audio caused by RF current on the shield of a microphone cable?
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.
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 Application
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.
Key Concepts
Why Other Options 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.
题目解析
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.
考试技巧
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.
记忆口诀
Ferrite choke = Filters RF on cables. Think 'F'errite 'C'hoke = 'F'ilters 'C'able RF. Blocks RF on shields while passing audio signals.
实际应用示例
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.
错误选项分析
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.
知识点
Ferrite chokes, RF feedback, Microphone cable interference, RFI suppression
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.