Question
What feature of a cardioid pattern antenna makes it useful for direction-finding antennas?
Answer Options
- A) A very sharp peak
- B) A single null
- C) Broadband response
- D) High radiation angle
Correct Answer: B
Explanation
A cardioid (heart-shaped) radiation pattern is synthesized from combining a loop antenna’s bidirectional pattern with a sense antenna’s omnidirectional pattern. This pattern is created specifically to solve the 180° ambiguity problem inherent in simple loop antennas used for direction finding (DF).
Its most useful feature for DF is a single null. This deep, singular point of minimum reception is unique to the cardioid pattern. By rotating the antenna until the null is found, the operator can precisely determine the direction from which the signal is originating without any ambiguity, as the pattern clearly points in one direction only.
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