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*Subject*: Re: [amsat-bb] 2.4 Ghz Helix--stacking distance*From*: "John Stephensen, KD6OZH" <kd6ozh@xxxxxxx>*Date*: Thu, 24 May 2001 07:31:02 -0000

I've been using the information published by John Kraus (second edition of "Antennas") to calculate spacing. helix directivity = 12 * circumference^2 * turns * turns spacing effective aperture = (directivity * wavelength^2) / (4 * pi) helix spacing = 2 * sqrt(effective aperture / pi) The antenna dimensions are in wavelengths. For three helices, I assumed that the effective aperture is circular and mounted them one aperture diameter apart. These equations reduce to: aperture diameter = diameter * sqrt(12 * turns * turns spacing) The diameter is in the same units as the spacing and the turns spacing is in wavelengths. For a square array you could assume that the effective aperture of each helix is square and get a smaller spacing: spacing = diameter * sqrt(3 * pi * turns * turns spacing) The calculated spacing works reasonably well. I haven't been able to detect any sidelobes when listening to the AO-40 beacon. 73, John KD6OZH ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Re: 2.4 Ghz Helix--stacking distance***From:*K5OE

**Re: 2.4 Ghz Helix--stacking distance***From:*Pieter Ibelings

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