Antenna Construction

In this section We will look at some different types of antenna. We will look at various types of antenna, And what types of antenna suit which bands. This is not intended to be a comprehensive manual on antennas, But a glimpse into the world of antenna’s. This article will only cover antenna’s for the purpose of signal reception, But will mention from time to time about transmitting on the antenna. This will only be done to illustrate the importance of some of the steps.

What is an antenna?

Simply put an antenna is any electrically conductive material. This includes things like… Wire , Coax, Aluminium, Copper, Brass, steel, even tin foil, etc.

Can I use any length for an antenna?

If you are using for receive only then yes. But it may not be an effective antenna. To be an effective antenna the length needs to be calculated for the frequency of interest. This is especially important if you wish to use the antenna to transmit on.

How do I calculate the correct Length of my antenna ?

This depends on the type of antenna, For most antenna’s the formula’s here will apply. There are some antenna’s like a discone antenna that use its own set of calculations (More on this type of antenna later in this series).

The following formula’s are the most common that are used in antenna building.

300/frequency (MHz) = antenna length in meters.

or

468/frequency (MHz) = antenna Length in feet.

Example 1: 300 / 145 MHz = 2.07 Meters.

Example 2: 468 / 145 MHz = 3.23 Feet.

Note:Both of these produce results for a half-wave antenna, which is the most common type of home-brew antenna.

Can I use any thickness material ?

The thickness of the material only matters if you want to transmit on the antenna. The thicker the material the more power output it will handle. If you use a thick material you may have to reduce the length of the antenna a little, But this will depend on how thick the material is, And the frequency its being used on.

Designing My First antenna

Important: Before starting to design any antenna, Go survey the location and check there are no power cables overhead or below the antenna location. You don’t want power lines to fall on the antenna or the antenna to fall on any power lines, during high winds.

Survey the general area and make sure there is enough space to fit the antenna in. Some antenna’s suit a small space, Others require a large area to construct properly. There is nothing worse than designing an antenna and not having the space to put it up and actually test its performance.

In My next Post…

Long wire and Dipole Antenna’s

Best Regards

Simon