Which alternative pairing best describes the information uniquely provided by secondary radar compared to primary radar?

Which alternative pairing best describes the information uniquely provided by secondary radar compared to primary radar?

• A. Identity and Altitude
• B. Bearing and Temperature
• C. Time and Frequency
• D. Mass and Volume

Answer: (B)

Secondary radar adds information that the basic echoes from primary radar do not reveal. The transponder in the aircraft replies to interrogations with data that uniquely identifies the aircraft (an identity code) and, if equipped, altitude encoded by the transponder (Mode C, and more with Mode S). Primary radar, by contrast, only shows where the object is in terms of range and bearing, with no inherent way to know who it is or how high it is. Since the distinctive, non-ambiguous details provided by secondary radar are the aircraft’s identity and its altitude, that pairing best describes what secondary radar uniquely contributes. Temperature isn’t a standard data element conveyed by radar, and bearing is something primary radar provides, not uniquely secondary. Time/frequency or mass/volume aren’t relevant to what secondary transponders deliver.

Secondary radar adds information that the basic echoes from primary radar do not reveal. The transponder in the aircraft replies to interrogations with data that uniquely identifies the aircraft (an identity code) and, if equipped, altitude encoded by the transponder (Mode C, and more with Mode S). Primary radar, by contrast, only shows where the object is in terms of range and bearing, with no inherent way to know who it is or how high it is. Since the distinctive, non-ambiguous details provided by secondary radar are the aircraft’s identity and its altitude, that pairing best describes what secondary radar uniquely contributes. Temperature isn’t a standard data element conveyed by radar, and bearing is something primary radar provides, not uniquely secondary. Time/frequency or mass/volume aren’t relevant to what secondary transponders deliver.