Tuesday 20 September 2011

LBA protype v 2.0

LBA platform version 2.0. Photo: Markku Postila
Here is another prototype of the raised LBA antenna platform designed by Markku Postila and Toivi Iinatti. This one allows arbitrary rotation of the antenna and has easily adjustable legs. The picture also shows the LBA antenna installed on top of the platform.

However, it seems that we will need to extend the ground plane with this type of a design. Recent antenna modeling results by Johan Borg of LTU suggests that this configuration has the effect of broadening of beam significantly at higher frequencies.

NEC model of the antenna with a raised ground sheet.
40 MHz beam pattern of an individual element. Slight broadening at 40 MHz, but nothing too serious.

80 MHz beam pattern of an individual element. The raised platform causes a broadening of the beam and a deeper minima at the zenith.

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