How does the capture area vary with different antennas?.

The presence of a capture area poses two important questions: For an amateur striving to achieve maximum gain, an antenna design utilizing half-wavelength spacings between elements can be termed inefficient! Achieving optimum spacings It should be noted that the customary half-wavelength spacing is a carry-over from collinear array design where no side lobes are desired.

With the increasing use of multielement Yagis, it became evident that longer Yagis had larger 'effective apertures,' and that in order to realize maximum gain when using two stacked Yagis, a spacing larger than the customary half wavelength was needed to insure that the respective capture areas were not 'overlapping.' The same effect was noted in the case of collinear dipoles, where a center-to-center spacing of approximately ¾ wavelength is needed to achieve maximum gain. The physical significance of this aperture is that the power from the incident plane wave is absorbed over an area of this size by the dipole, and is delivered to its terminating resistance. The maximum effective aperture of a dipole is approximately the same as an area ½ by ¼ wavelength on a side. This area is called ' effective aperture,' and more often 'capture area.'Īs an example, consider the dipole. enthusiasts, have become aware that an antenna, no matter how small it is physically, has associated with it a power-gathering area. The first part of this article is a brief review of the original material, while the second part presents practical antenna designs fashioned in response to various inquiries. The following words of wisdom were assembled to assist these people. In the April, 1958 issue of QST, the author presented an article entitled ' Optimum stacking spacings in antenna arrays.' It soon became evident that although basic terms and fundamental equations were used in an effort to attain simplicity, many people did not grasp the meaning of the concepts presented nor were they able to utilize these concepts in a practical antenna design. Here's down-to-earth information on putting together multi-antenna arrays complete with universal design charts and examples of how to use them. Stacking two antennas doesn't always result in a 3 dB, gain improvement - it all depends on the spacing used. Getting the most gain from stacked antennas. Home - Techniek - Electronica - Radiotechniek - Radio amateur bladen - QST - Array design with optimum antenna spacing

Cubical quad gain