BDA is an array of a number of equal parallel elements (conductors) with their central parts connected together with an air insulated transmission line or an open wire if you will. BDAs can be positioned either in horizontal plane (like Yagi) or in vertical plane (like stacked dipoles). The former orientation ensures lower wind load, the latter - higher gain.
Despite its simplicity, it covers 14 - 30 MHz with a reasonable SWR. When positioned in the horizontal plane, the antenna looks like in the drawing below.
When positioned in the vertical plane, the antenna looks like in the drawing below.
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An additional element brings the SWR down below 3:1 when measured at the feed point.
Please note that from now on, only the horizontal position will be shown in the drawing, but the simulation results will be presented for both orientations.
The antenna performance when positioned in horizontal plane.
The antenna performance when positioned in vertical plane.
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This version of BDA shows slight improvement in gain for the horizontal plane orientation.
The antenna performance when positioned in horizontal plane.
The antenna performance when positioned in vertical plane.
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And finally - the 5-element version. Despite having that many elements, its depth is the smallest - only 1.6 m.
The antenna performance when positioned in horizontal plane.
The antenna performance when positioned in vertical plane.
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This variant of the BDA covers 10.1-29.7 MHz range. XF stands for "eXtended Frequency". I modeled 4-element version and 5-element version. The former had better performance, so I am presenting below only the 4-element version. Please mind that due to its length, nearly 12 meters, it is more difficult to construct than the other BDA variants. But getting one extra band might be worth the effort.
The antenna performance when positioned in horizontal plane.
The antenna performance when positioned in vertical plane.
Click here to download this antenna models.