Antenna Height Effect on Radiation Angle
The angle of radiation from an antenna is the angle above the horizontal at which the radio waves are transmitted into space.
Key Relationship:
- Increasing the height of an antenna generally leads to a decrease in the angle of radiation.
- Conversely, decreasing the antenna height tends to increase the angle of radiation.
Reasoning:
A lower angle of radiation is desirable for long-distance communication (skywave propagation) because it allows the radio waves to travel further before hitting the ionosphere and reflecting back to Earth. Higher antennas achieve these lower angles more effectively.
Therefore, if the height of an antenna increases, the angle of radiation naturally decreases.
Important Questions from Basics of Antenna
The angular distribution of the transmitted power around the antenna is generally known as :
An antenna is polarized in the plane of the field perpendicular to
The value of radiation resistance of a Hertzian dipole of length \(\dfrac{\lambda}{80}\) is given by
What should be the length of transmitting Antenna for radiating radio waves of 900 MHz
An antenna is generally a metallic object, often a wire or collection of wires, used to convert high frequency current into electromagnetic waves and vice-versa. Antenna serve either or both of the following two functions, generation or the collection of electromagnetic energy. In a transmitting system, a radio-frequency signal is developed, amplified, modulated and applied to the antenna. The R-F currents flowing through the antenna produce electromagnetic waves which radiate into the atmosphere. In a receiving system, electromagnetic waves "cutting" through the antenna induce alternating currents for use by the receiver.
Efficient operation also requires that the receiving antenna be of the same polarization as the transmitting antenna. Polarization is the direction of the electric field and is therefore, the same as the antennas physical configuration. Thus vertical antenna will transmit vertical polarized light, any antenna having a physical length that is one-half wavelength of the applied frequency is called a Hertz antenna. Hertz antenna are predominantly used with frequencies above 2 MHz. Usually, at frequencies below 2 MHz, a Marconi type of antenna is used. The Marconi antenna is usually a quarter-wave grounded antenna or any odd multiple of a quarter wavelength.
The Yagi-Uda antenna consists of a drivers element and two or more parasitic elements. Yagi-Uda has two parasitic elements, a reflector and a director. This Yagi-Uda antenna provides about 7 dB of power gain with respect to a half-wavelength dipole reference. More complex antennas may be circularly polarized both vertically and horizontally polarized waves are radiated with equal power in both. If the powers are unequal the antenna is said to be elliptically polarized.
A horn is an ideal antenna for terminating a waveguide and may be conical, rectangular or sectorial. Wide band antennas either when the transmissions are wide band or when working of narrow channels over a wide frequency range is the major application. Helical antenna, which consists of a loosely wound helix backed up by a metal ground plane. Loop antennas are often used for direction finding. Loops have many shapes and generally consists of a single turn of wire. Discone is a ground plane antenna evolved from the vertical dipole and having a very similar radiation pattern.
