Antenna, RF feeder and RF connector topics

RF antennas (or aerials) are an essential element of any radio communications link, whether it is for a high power transmitter like those used for broadcasting, or low power ones like those used wireless technologies such as WLAN or remote control and sensing applications. Apart from the power levels, RF antennas are used across the whole radio spectrum, from ELF right up to the microwave bands. Whatever the power, and the frequency, the basic RF antenna design theory remains the same, although the practical approach has to change to meet the differenting mechanical requirements.

Although RF antenna design and theory can involve a considerable amount of involved mathematics, there is much that can be achieved with only a minimum of mathematics, and most RF antenna engineers do not need a Ph.D in advanced calculus.

RF Antenna Basics

Electromagnetic waves and basic antenna operation
Polarisation
impedance - including radiation resistance, loss resistance and efficiency
Resonance and bandwidth
Directivity and gain

Feeders

The ideal position for an antenna is rarely in the optimum position for the transmitting or receiving equipment. As a result a form of transmission line or feeder is required to transfer the signals and power to and from the antenna.

Coaxial feeder
Coax cable loss or attenuation the reasons for it and how to minimise it.
Coax cable power rating
Coax cable velocity factor
RF coax cable data and specifcations
Environmental factors relating to coax cables
Balanced feeder
Waveguide basics
Waveguide data
Antenna RF diplexer - although not a feeder, a diplexer is sometimes included in the feed system of an antenna.
 

RF coax cable connectors

A wide variety of RF connectors are available for making connections to coaxial cable. These connectors including BNC, C-type, N-type, UHF (Amphenol) connector, SMA, SMB, SMC and many more are able to be used in a variety of applications.

Coax cable connectors - general overview
BNC connector
TNC connector
C-Type connector
N-Type connector
SMA connector
SMB connector
UHF connector
 

The dipole antenna

The dipole antenna is one of the most basic forms of antenna available. It is widely used on its own, and it is also used as the "driven" element in many other types of antenna.

The dipole antenna
Folded dipole
 

The vertical antenna

Vertical antennas are widely used in many areas, and are particularly widely used for mobile applications because they radiate all around them in the horizontal plane. This means that they do not need redirecting as the mobile station moves. The quarter wave vertical is the simplest, but there are many other designs that provide improved performance and gain.

Quarter wave vertical
Five eighths wavelength vertical
J pole vertical antenna

Directional antennas

There is a good variety of different types of directive antenna that can be used. Although the yagi antenna is the most popular, it is by no means the only one, and other designs and approaches are more applicable in many instances.

Yagi
Log periodic beam antenna
Parabolic reflector
Horn antenna
 

Wideband antennas

Most antennas are only able to operate over a narrow bandwidth. There are some techniques that enable the bandwidth of an antenna to be increased considerably, and also some desgigns that are able to operate over very wide bandwidths.

Discone
Log periodic beam antenna
 

Loop antennas

Where directivity and small size are required, loop antennas may often provide an answer. Although different types of loop have slightly different properties, they are able to provide a good antenna solution in many circumstances.

Loop antenna overview
Ferrite rod antenna
 

Applications

Antennas can be used in many applications from reception of terrestrial and satellite television to point to point radio, short wave radio and much more.

Satellite antennas for satellite television and other satellite applications
 

Antenna installation

When installing an antenna many points must be considered. Location, type of antenna, method of installation and many other items all affect the antenna installation. Safety is also a crucial element because if the antenna is not installed correctly the antenna may collapse.

Antenna height
Antenna installation materials - choosing the correct materials to minimise corrosion
How to install coax cable - some key points to note