Radiation Pattern of Mobile Antennas
Most people think that antennas mounted on vehicles are omnidirectional. This is mostly true, but the radiation pattern is influenced greatly by the body of the vehicle. Remember we stated that the body acts as the "radials" for the antenna? Well, we know that the body does not extend around the base on the antenna equally. Figure 2 shows how the radiation pattern of a whip is influenced by the body of the vehicle. As you can see, the shape of the pattern depends on where you mount the antenna. The pattern is "pulled" to areas where there is the most vehicle body. The pattern is the worst in directions where there is no metal body for a radial.
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