Overview Dipole Antennas
Tuned half-wave dipoles have been among the most important antennas from
the beginning of rf-technique. The characteristics of half-wave dipoles
have been calculable very early using the Maxwell and Hertz equations.
Therefore the half wave dipole became a reference antenna.
The ideal (lossless) half-wave dipole has an isotropic gain of 2.15 dBi
and an impedance of 73 Ohm. The directional pattern is circular in the
H-plane, "8-shaped" in the E-plane with the maxima perpendicular on the
dipole axis.
The half-power beamwidth (-3 dB) is approx. 78�.
The impedance of real dipoles is depending on the thickness/length ratio
of its elements, typical values are 60-70 Ohm.
Dipoles for industrial applications are available in the frequency range
from 30 MHz to up to approx. 4 GHz. The dipole elements are length
variable (telescopic) or with fixed length, the latter especially above
1 GHz.
The most important applications are test site evaluations (NSA,
normalized site attenuation) and the determination of ERP (Effective
Radiated Power) respectively EIRP (Effective Isotropic Radiated Power).
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