What type of encoding is used by a Mode C transponder transmission to ATCRBS ground stations?

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Multiple Choice

What type of encoding is used by a Mode C transponder transmission to ATCRBS ground stations?

Mode C replies to ATCRBS interrogations use a train of very narrow, fixed-width pulses, and the information is carried by when those pulses occur in time. This is Pulse Position Modulation—the timing of each pulse encodes the bits that make up the squawk code plus the altitude data. The pulse amplitudes stay essentially the same, and the ground station decodes the message by measuring the intervals between pulses, not by changing amplitude or using phase. Other methods like changing the carrier phase or amplitude aren’t how Mode C encodes the reply.

Mode C replies to ATCRBS interrogations use a train of very narrow, fixed-width pulses, and the information is carried by when those pulses occur in time. This is Pulse Position Modulation—the timing of each pulse encodes the bits that make up the squawk code plus the altitude data. The pulse amplitudes stay essentially the same, and the ground station decodes the message by measuring the intervals between pulses, not by changing amplitude or using phase. Other methods like changing the carrier phase or amplitude aren’t how Mode C encodes the reply.

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