In which direction or directions does an electrically small loop (less than 1/10 wavelength in circumference) have nulls in its radiation pattern?
The correct answer is B: Broadside to the loop. The direction or directions in which an electrically small loop (less than 1/10 wavelength in circumference) has nulls in its radiation pattern is broadside to the loop. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. For amateur radio operators, this is important for direction finding. Understanding this helps when using loop antennas.
Exam Tip
Small loop nulls = broadside to the loop. Think 'S'mall 'L'oop = 'S'ignal 'L'owest 'B'roadside. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. Not in the plane, not both, not omnidirectional - just broadside.
Memory Aid
"Small loop nulls = broadside to the loop. Think 'S'mall 'L'oop = 'N'ulls 'B'roadside. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. Important for direction finding."
Real-World Application
An electrically small loop antenna: The loop has nulls (minimum radiation) broadside to the loop - perpendicular to the plane of the loop. This is why loops are used for direction finding - you can rotate the loop to find the null direction. Small loops have nulls broadside - this is their radiation pattern characteristic.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Nulls aren't in the plane of the loop - they're broadside (perpendicular) to the plane. In the plane is wrong.
Option C: Incorrect. Nulls aren't both broadside and in the plane - they're only broadside. Both is wrong.
Option D: Incorrect. Small loops aren't omnidirectional - they have nulls broadside. Omnidirectional is wrong.
题目解析
The correct answer is B: Broadside to the loop. The direction or directions in which an electrically small loop (less than 1/10 wavelength in circumference) has nulls in its radiation pattern is broadside to the loop. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. For amateur radio operators, this is important for direction finding. Understanding this helps when using loop antennas.
考试技巧
Small loop nulls = broadside to the loop. Think 'S'mall 'L'oop = 'S'ignal 'L'owest 'B'roadside. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. Not in the plane, not both, not omnidirectional - just broadside.
记忆口诀
Small loop nulls = broadside to the loop. Think 'S'mall 'L'oop = 'N'ulls 'B'roadside. Small loops have nulls (minimum radiation) broadside (perpendicular) to the plane of the loop. Important for direction finding.
实际应用示例
An electrically small loop antenna: The loop has nulls (minimum radiation) broadside to the loop - perpendicular to the plane of the loop. This is why loops are used for direction finding - you can rotate the loop to find the null direction. Small loops have nulls broadside - this is their radiation pattern characteristic.
错误选项分析
Option A: Incorrect. Nulls aren't in the plane of the loop - they're broadside (perpendicular) to the plane. In the plane is wrong. Option C: Incorrect. Nulls aren't both broadside and in the plane - they're only broadside. Both is wrong. Option D: Incorrect. Small loops aren't omnidirectional - they have nulls broadside. Omnidirectional is wrong.
知识点
Electrically small loop, Nulls, Broadside to the loop, Radiation pattern
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.