How does a noise blanker work?

A noise blanker (NB) is a receiver circuit designed to eliminate short, repetitive, broad-spectrum noise pulses, such as those caused by automotive ignition systems or power line arcing. It achieves this by detecting the sharp rise time of an incoming noise spike and momentarily reducing the receiver's gain, essentially muting the intermediate frequency (IF) stage. Because these noise pulses are extremely brief—often lasting only a few microseconds—the receiver is effectively 'turned off' for just a tiny fraction of a second. This interruption is so short that the human ear cannot detect the missing audio, but the loud, distracting pop or click of the interference is successfully prevented from reaching the speaker. It is important to distinguish a noise blanker from a noise limiter. Option D, 'clipping noise peaks,' describes a noise limiter, which chops off the top of an audio wave after it has been demodulated. A noise blanker operates much earlier in the signal chain by turning down the receiver gain entirely during the pulse, making Option C the correct answer.