Contents
How do I check antenna impedance?
Antenna impedance is a complex quantity (i.e. real+imaginary). It is typically measured with a Network Analyzer. A multimeter will only give you the real impedance and will only give it at DC. At DC, most actual antennae have zero (ideally) real resistance.
What is a Hertzian dipole?
An infinitesimal element excited with an alternating current is called the Hertz dipole. In practice a linear antenna can be approximated by a Hertz dipole if the linear antenna is of size much smaller the wavelength. The Hertz dipole is oriented along the z-axis, has length and current .
What is the impedance of a half wave dipole antenna?
This website http://www.antenna-theory.com/antennas/halfwave.php says if you reduce the antenna from 0.5 to 0.48 of a wavelength then that will compensate for the reactive part and remove it, leaving you with a pure 70 ohm resistance. The theoretical impedance of a half wave dipole antenna is 73 + j 42.5.
What is the impedance of a quarterwave monopole?
The impedance of monopole is half of its virtual dipole’s impedance. For example a quarterwave monopole with ground planehas impedance of 36 ohms, which is half of 75 ohms, the impedance of its virtual dipole, the halfwave dipole. The impedance of a dipole varies very sharply when its length is fullwave.
What kind of Feeder does a half wave dipole use?
A half wave dipole is often fed with a 50Ω feeder. The antenna often presents a very good match tot his because the proximity of other objects, like the Earth, antenna mounting, etc. means that the impedance is lowered below the 73Ω it presents in free space.
Which is the shortest wavelength of a half wave dipole?
As the name implies, the half wave dipole is a half wavelength long. This is the shortest resonant length that can be used for a resonant dipole. It also has a very convenient radiation pattern.