Question 13B6

A noise blanker circuit operates by identifying sharp, fast-rising noise pulses, such as those from vehicle ignition systems or power lines. When such a pulse is detected, the blanker generates a short gating pulse. This gating pulse is then applied to an Intermediate Frequency (IF) amplifier stage within the receiver. For the brief duration of the noise pulse, the IF amplifier's gain is momentarily reduced, or the stage is completely shut off. This effectively "blanks out" the noise pulse from the signal path *before* it can be fully processed and demodulated into audio, significantly reducing its perceived annoyance. Option A is incorrect because a simple limiter circuit continuously clips signal peaks, which can distort the desired signal, unlike the pulsed gating action of a noise blanker. Option C is incorrect because blanking at the ratio detector (an FM demodulator) is too late in the signal chain to effectively remove the noise pulse itself, which would have already impacted earlier stages. Option D is incorrect as it's typically more practical and effective to perform blanking in the IF stage, where the noise pulse's characteristics are easier to isolate and gate compared to the broadband RF stage.