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J-Pole Antenna Question
Hello,
Are vertical J-Pole VHF antennas (essentially) omni directional in coverage ? Thanks |
#2
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J-Pole Antenna Question
On Jun 17, 9:46 am, "Robert11" wrote:
Hello, Are vertical J-Pole VHF antennas (essentially) omni directional in coverage ? Thanks Yes it is omnidirectional. This antenna is merely a 1/2 vertical end- fed with a 1/4 wave matching stub. Frank K3YAZ Tucson |
#3
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J-Pole Antenna Question
"Robert11" wrote in message ... Hello, Are vertical J-Pole VHF antennas (essentially) omni directional in coverage ? No. A J-Pole is not an isotropic radiator. It is "omnidirectional" only if you consider signals that intersect the antenna in the plane that is at a right angle to the major axis of the antenna. The closer you get to having the signal intersect the antenna at the end the the less sensitive the antenna is. i.e. it is less sensitive to transmissions that are from below or above the antenna. You will get an idea of the plot the antenna's free space pattern if you imagine an orange with two major parabolic dimples 180 degrees apart, the centers of which are in line with the major axis of the antenna. In practice the antenna is considered an omni because they are mounted vertically to communicate over the surface of the earth with other radio units on the surface of the earth .In day to day operations the surface of the earth is very close to the geometric defintion of a plane. Dan AI8O |
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