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most handy for dipoles, it is made much shorter—say a few
centimetres? The radiation from a single dipole is of course limited
by its size, and to bring the e.r.p. (Sec. 17.11) up to a useful figure a
relatively large reflector is needed. Instead of an enormous number
of small dipoles, it is made of continuous metal, or, to reduce weight
and wind resistance, wire netting. The currents induced in this by the
driven dipole cause reflection, but in a more controllable pattern, for
the metal can be formed into a parabolic reflector, like a large
headlight or bowl heater, usually called a dish. In this way the
radiation or reception can be confine ...