[TowerTalk] supergain

[K4SB]

rick@area.com wrote:
> 
> A quick note here on what the theoreticians say about "supergain"
> which they call "superdirectivity".   This discussion assumes lossless
> elements and matching networks (for now).  The most gain you can get
> additively is a power gain of N (in dB 10 log N) for N elements.  This
> occurs for spacings of around 1/2 wl.  When you go to closer spacing,
> for an optimum driven array, the maximum achievable gain goes up, due
> to subtractive gain.  Unlike the Yagi principle that gain is proportional
> or whatever to boom lenghth, the driven array optimized for maximum gain
> just gets more and more gain as the spacing is decreased.  This is no
> theoretical limit to this gain.

Oops, not quite so. Maximum gain occurs when the spacing is so
infinitly small as to require gold elements in a controlled
temperature environment. From Maxwell, Volumn 1 ( And yes, the
feedpoint impedence is almost 0, which is why
you must use gold to reduce resistance of the array. ) I think (
old memory )
the W8JK rig was based on this principle, and then modified.

73
Ed

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