ARRL Technician Practice Exam

Which of the following could you use to cure distorted audio caused by RF current flowing on the shield of a microphone cable?

1. Belt clip

2. RF filter

3. Ferrite choke

4. Inline attenuator

The correct answer is: Ferrite choke

Using a ferrite choke is effective for curing distorted audio caused by RF current flowing on the shield of a microphone cable because it helps eliminate unwanted RF interference. Ferrite chokes function by introducing a high impedance to high-frequency RF signals, which dampens their ability to travel down the cable. This is particularly useful in preventing RF currents from affecting the audio signal, resulting in clearer sound quality and reducing the distortion that can occur when RF energy interferes with audio equipment. The other options do not address the issue as effectively. For example, a belt clip has no impact on electrical interference; it is merely a physical accessory for securing the microphone. An RF filter might be beneficial in certain contexts, but it typically operates on a different principle, and might not provide the necessary isolation from RF currents directly on the microphone cable shield. An inline attenuator reduces the strength of the audio signal, which may not resolve the underlying issue of RF interference causing distortion; instead, it could potentially worsen audio quality by lowering the signal without removing the interference. Overall, the use of a ferrite choke is specifically designed to combat RF noise while maintaining the integrity of the audio signal.