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RF BASICS: ANTENNA TYPES AND CHARACTERISTICS
Date:2018-01-18 11:42:00   Browse:146


What is the purpose of an antenna?

An antenna is used to convert electric energy into radio waves which enables communication/ instruction between two points. These are usually a radio transmitter and receiver- no radio device will work without one. Depending on the application, antennas can sometimes be as simple as a piece of wire. They work when radio waves reach an antenna and cause the electrons inside it to vibrate. This creates an electric current that duplicates the original signal.


What is Gain?

Gain is a key performance indicator which combines an antenna’s directivity and electrical efficiency. Gain describes how well the antenna coverts input power into radio waves headed in a specified direction or vice versa. Essentially, it refers to how well the antenna works to receive or transmit a signal compared to if you didn’t have one.


Gain is measured in Decibels (dBi) and the larger the dBi, the more gain it has. High gain antennas are useful for manipulating the signal to go further in one direction and less in another, but do not increase the signal strength overall. For example, using a high gain antenna on your wifi router would improve the signal reach on the floor it’s on, but rooms on other floors of the house are likely to have some trouble connecting to the internet.


Directional or Omnidriectional?

Most antenna can be catagorised as either directional or omnidirectional. Omnidirectional antennas receive and transmit at a 360 degrees radius, radiating powder uniformly in all directions on one plane. This type on antenna is usually pole-shaped and situated on a metal plane (car roof, for example,) which acts as the bottom half of the dipole. They are commonly used for GPS applications, vehicles and emergency radio and have a higher gain in horizontal directions.


Directional antennas primarily receive and transmit energy from one direction. The most common type of directional antenna is the Yagi- it’s usually used as a TV aerial and promotes energy in one direction, using multiple prongs to encourage overall gain. Directional antennas are good for home/business use as you can tune system for optimal coverage. With directional antenna, the more focused the energy (the smaller the percentage of 360 degrees that the signal radiates,) the larger it’s the reachable distance.


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