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Folded Dipole Orientation

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BlueDevil

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What options are available to align the array of elements in a folded dipole antenna? Must the array be all pointing in the same direction or each 90 degrees offset from the next?

Could a folded dipole antenna be setup so that it provides 180 degree coverage with each element roughly 45 degrees offset from the next?
 

WA0CBW

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I assume this is for VHF/UHF frequencies. A folded dipole (or any dipole) radiates broadside to the length of the dipole. At VHF/UHF frequencies the dipole is mounted vertically and can have several dipoles mounted above/below each other on the same mast connected by a phasing harness. Each dipoles radiation pattern is omni-directional. Pointing each dipole in a different direction around the mast can change the radiation pattern from omni-directional to directional. This type of antenna is found in most commercial radio antenna installations.
BB
 
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BlueDevil

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This is a commercial application VHF base repeater antenna with 4 elements.
 

prcguy

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On your 4-bay dipole array its typical to get 9dBD gain in a 90 to 120 degree pattern if all the dipoles are lined up on one side. If you stagger the elements 90deg so one is aimed north, one east, one south and one west it will give you an omni pattern with about 6dBD gain. You can also put a pair on each side 180deg apart and make a bi-directional pattern.
prcguy


This is a commercial application VHF base repeater antenna with 4 elements.
 

BlueDevil

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I think this is the radiation pattern of the way I currently have my elements aligned. Correct me if I am wrong because I could be reading the description wrong.

60f2d641d150105b30f9897ca461590e.jpg



Cheers,

Brandon
 

prcguy

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If all the elements are lined up on one side of the mast AND you have the elements spaced 3/8 wavelength out from the mast, that will be your pattern. You didn't mention the brand of dipole array and to my knowledge Telewave is the only brand that lets you space the elements at different distances out from the mast to further modify the pattern.

Most dipole array antennas have the dipoles fixed at much less than 1/4 wavelength and closer to 1/8 wavelength from the mast and that is not adjustable. That would give you a pattern different than what you posted but the east and west points will be similar and the north point will be filled in instead of degraded about 2dB like on the chart.
prcguy


I think this is the radiation pattern of the way I currently have my elements aligned. Correct me if I am wrong because I could be reading the description wrong.

60f2d641d150105b30f9897ca461590e.jpg



Cheers,

Brandon
 

BlueDevil

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I am using an RFS-340 antenna. The manufacture only provides the radiation pattern for directional and omni directional. However after making contact with the manufacture they said that the antenna could function like I have it setup, they just don't have a radiation pattern for that alignment.
 
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