Introduction
A Yagi antenna is a type of directional antenna. They were very common over the past half century to receive over-the-air transmission signals, particularly radio and television. Yagi antennas are quite complex and are still being used today in areas where cable or satellite television is not common.
Yagi Antenna Components
Each Yagi antenna consists of dipoles, reflectors and directors. A dipole antenna receives radio frequency energy in a circular field ending at the center of the dipole. The Yagi antenna uses a series of dipoles in order to allow for a wider range of single to reach the antenna. With a Yagi antenna all parts of the antenna usually lay on the same plane. This can be extremely useful, especially with more modern Yagi antennas. The more dipoles that the Yagi antenna has on the same plane, the more bands of signal it can pick up at the same time.
Basic Yagi Antenna Design
Yagi antennas are made to focus in one direction, forward. All waves in the other direction are canceled out. The driven element, which allows for signal to be amplified in one direction, is longer than the director elements. Yagi antennas take advantage of this and have several parasitic elements which hookup to the driven element and allow for increased gain. The parasitic elements then aim the antenna in the correct direction in order for the antenna to have the best possible reception. With the Yagi antenna, each element adds up and builds on to the antenna's ability to gain even more signal. In some Yagi antennas, the director element is cut too short and has to be carefully placed around one half wavelength away in order for it to remain useful to the antenna. Yagi antennas with more elements can receive signals with a longer wavelength.
Receiving Multiple Frequencies
Yagi antennas are commonly being used on multiple frequencies. This requires that they have several different traps in order to get a wide array of different signals. The highest frequency trap used on an antenna needs to be as close as possible to the boom, with the traps radiated outward from the boom in order to get all the bands of signal that are required. However, traps do have some downsides on Yagi antennas. For example, they reduce the overall bandwidth and efficiency of the antenna. However, traps are needed to get the maximum amount of signal possible.
Summary
Yagi antennas are one of the most common types of antennas. They are used for a wide range of activities including ham radio and receiving over-the-air television signals. They work by using a large number of dipole elements to receive the widest range of signal possible. Yagi antennas are able to stop signal interference and receive more than one band of signal at the same time.
Tags: Yagi antennas, Yagi antenna, bands signal, being used, driven element