VHF 5/8wave vertical antennas

Posted on Jan 10, 2013

At VHF, both the 1/4-wavelength monopole and the 5/8-wavelength monopole antennas are widely used. The VHF 5/8-wavelength (144 Mhz) vertical monopole has long held the reputation of providing about a 3-dB gain advantage over the 1/4-wavelength vertical monopole. The foundation of that reputation rests upon theoretical calculations that show the longer monopole to have the derived gain increase when both monopoles are set over a perfect ground.

VHF 5/8wave vertical antennas
Click here to download the full size of the above Circuit.

A second factor contributing to the reputation of the longer monopole for higher gain is the current distribution along the element. Next Fig shows the distribution for both the long and short monopoles, with the ground plane elements omitted for clarity.

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