Design a Simple Antenna
This article will show you how to build a monopoly for any use you see fit.
Steps
- Find out what frequency you want (for Wi-Fi you are using 2.45GHz = 2,450,000,000Hz). This is needed because this determines the length of your antenna.
- Get a good conductor. For the example we can use a copper wire and a piece of copper plating. Also you will need a co-axial cable (75 ohm is better than 50 ohm, for Wi-Fi 50 ohm is better than 75 ohm).
- Work out the length you need the wire to be. This is done by using the frequency value from step 1 to find the wavelength of the signal. To do this you simply need to divide the speed of light (c = 299 792 458 m/s) by the frequency (f). In the case of 2.45GHz the wavelength is {{safesubst:#invoke:convert|convert}}. Usually monopole antennas are quarter-wavelength structures, so the length of the wire should be 12.236/4 = 3.0509cm
- Cut the wire a little bigger than you need, about {{safesubst:#invoke:convert|convert}} or so. This way you can pare it back based on performance.
- Form a "Ground-Plane". This is basically used to form a theoretical mirror image of the antenna. Simply use the copper plate that you picked up earlier. It should be at least half a wavelength square.
- Drill a hole in the center of the plate just big enough for the co-axial cable to fit through.
- Pare the Co-ax cable to reveal it's ground [outer conductor], which can be pulled back to reveal the inside insulator.
- Push the cable through so that the start of outer insulation is flush with the hole. The ground conductor is now above the ground-plane. Fold the ground conductor back and solder it to the copper ground plane.
- Pare the inside insulation back to reveal the signal conductor.
- Solder the copper wire to the signal conductor of the co-ax.
Tips
- The radiation pattern is null at the tip of the wire so make sure that you keep the antenna perpendicular to the source of the radio signals
- Make sure the wire is perpendicular to the ground plane
- The Antenna has a pretty much circular pattern when viewed from the top, so it should pick up your signal no matter where you decide to place it.
Warnings
- If you short the GND and the signal wire you'll be in trouble.
- Don't let it get wet, as this frequency is not "friendly" to water.
Things You'll Need
- Coaxial Cable
- Copper Plate
