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Gain per unit length of boom

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October 19th 04, 08:50 AM

Ian White, G3SEK

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wrote:

The above extract is lost on me as I was looking for maximum gain per
unit boom length based on NEC without regard to number of elements
required to attain that gain. Thus increases or decreases from
critical
coupling
can be ascertained..

You misunderstand what this curve is telling you.

There is a general law that gain is proportional to "aperture area". For
something like a dish, "aperture area" is the frontal area of the dish
itself (multiplied by an efficiency factor 1). For long yagis,
"aperture area" is roughly proportional to boom length.

This concept has nothing whatever to do with NEC! But it is the absolute
bedrock of all antenna engineering. What you really need right now is to
read the first few chapters of Kraus... and understand these most basic
principles.

NEC calculations will not tell you anything about this. NEC is simply a
tool to calculate what the gain of a particular antenna will be (or can
be, if you build it as modeled).

--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

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