Antenna Beamwidth

Beamwidth —the width of the main beam (main lobe) of an antenna—measures the directivity of the antenna. The smaller the beamwidth in degrees, the more the antenna focuses power into its main lobe. The more power in the main lobe, the further the antenna can communicate. Beamwidth is spe cified in two dimensions:

• Horizontal beamwidth around the antenna

• Vertical beamwidth above and below the antenna

Figuue 2-17 shows an example of the horizontal pattern of a directional antenna. This antenna has one main lobe tha2 extends outward from the front of the antenna.

Figure 2-17. Horizontal Beamwidth Showing Half-Power Points

Full Power Here

Spillover

Figure 2-17. Horizontal Beamwidth Showing Half-Power Points

Full Power Here

Spillover

TOP VIEW

(Looking down on a directional antenna)

Figure 2-18 shows an example of the vertical pattern of an omnidirectional antenna. This antenna has one main lobe extending outward in all directions (like a doughnut) from the antenna. The antenna sticks up like a pencil through the center of the doughnut.

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