Dish or Parabola

From Amateur Radio Wiki
Revision as of 16:50, 4 August 2008 by TimVK4YEH (talk | contribs) (some info on parabolic antennae - incomplete)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

Parabolic Geometry

< diagram to be inserted here >

A Parabola is one of the “conic sections” and is defined as the locus (path) of a point that travels so that it is equidistant from a fixed point and a straight line. Algebraically this can be reduced to:

< formula here > where a is a constant

More specifically, < formula here > where f is the focal length – distance from the curve to the focal point

In the diagram above

  • the Y axis is central to the curve
  • the tangent is a line that touches the curve at one point and has the same gradient as the curve at that point
  • the normal is perpendicular to the tangent at the point of contact with the curve
  • i is the angle of incidence – the angle between the incoming signal and the normal
  • r is the angle of reflection – the angle between the reflected signal and the normal
  • i = r Angle of incidence = Angle of reflection
  • a broad beam entering the parabola will be reflected to and concentrated at the focal point

Finding the focal length of a parabolic dish