GeneralG9C08

What is meant by the “main lobe” of a directive antenna?

D
Answer
Antennas and feed lines
Type
A
The magnitude of the maximum vertical angle of radiation
B
The point of maximum current in a radiating antenna element
C
The maximum voltage standing wave point on a radiating element
D
The direction of maximum radiated field strength from the antenna

Answer Notes

Directional antennas focus their radiated energy in specific directions, creating a radiation pattern made up of various "lobes." The "main lobe," also known as the major lobe, is the specific direction in which the radiated field strength is at its absolute maximum. This is the primary direction the antenna is "pointing." Other, smaller areas of radiation in the pattern are called minor lobes, which include side lobes and the back lobe. The goal of a directive antenna is to maximize the main lobe while minimizing these secondary lobes. Distractors mentioning maximum current or voltage points refer to the electrical standing waves on the physical antenna elements themselves, not the radiated electromagnetic field in space. Similarly, the vertical angle of radiation is a measurement of the lobe's elevation, not the definition of the lobe itself.
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In free space, how does the gain of two three-element, horizontally polarized Yagi antennas spaced vertically 1/2 wavelength apart typically compare to the gain of a single three-element Yagi?