ARRL Technician Practice Exam

Which of the following would reduce ignition interference to a receiver?

1. Increase the RF gain

2. Turn on the noise blanker

3. Change the microphone

4. Disconnect the battery

The correct answer is: Turn on the noise blanker

Turning on the noise blanker is effective in reducing ignition interference to a receiver because noise blankers are specifically designed to suppress impulsive noise, which is often generated by electrical devices such as spark plugs and ignition systems in engines. These devices can create sharp voltage spikes that lead to interference in radio reception, particularly in the HF (High Frequency) and VHF (Very High Frequency) bands typically used by amateur radios. The noise blanker works by sensing these abrupt changes in signal amplitude and applying a form of noise reduction, allowing the receiver to filter out the undesired impulses while retaining the desired audio signal. This helps improve clarity and reduces the overall noise floor, making it easier for operators to hear communications over the disruptive interference. The other options, such as increasing RF gain or changing the microphone, would not specifically address ignition interference and could potentially worsen the situation by amplifying the noise. Disconnecting the battery would completely disable the receiver, thereby preventing any reception, which is not a viable solution for reducing interference.