15 Element Yagi Wifi Antenna (Part 1)

Solid connectivity with commonly available parts.

YAGI WIFI ANTENNA DESIGN:

Sometimes the perfect antenna for a wifi network is the one that can be made in an hour's time, is made of inexpensive parts, and yet enables connections over moderate to long distances. The yagi wifi antenna project depicted here is exactly that! It is computer designed, made of wood and wire, and provides over 15 dB gain.

Yagi antennas can be rather difficult to make - elements must be cut to the proper length, and spaced at the correct distance from other elements, or the antenna doesn't work. Before good computer tools were available, a designer used various charts and tables to determine antenna dimensions. These days, however, much of the mind numbing calculation can be carried out in a split second. One excellent tool for crunching design numbers is the W9CF yagi antenna modeler

The on-line antenna modeler initially starts with several examples tailored for operation in the amateur bands. One of the best designs is the classic K1FO yagi. By following a few steps, it can be scaled for 802.11 b/g/n frequencies:

1. Start with the 15 element K1FO 70cm example
2. In the "units" menu, select "Radians."
3. Move to the "frequency" field and enter "2450" for the center of the wifi networking band.
4. Click the "calculate" button.
5. In the "units" menu, select "millimeters."
6. Move to the "element diameter" field and enter "1.7" for the diameter of 14 AWG wire.
7. Click the "calculate" button.
8. In the file menu, select "list elements."

The elements list will show each element, from the director (element 1, position zero mm), to the last director (element 15, position 418.5 mm). Any changes in element diameter, design frequency, will need recalculation and the new elements list checked.

Below is a graphic adapted from the modeler which shows element lengths and positions along the boom, measured from the director (location zero millimeters). Note that the driven element is depicted in green, and for the wi-fi yagi project, will be a folded dipole. Why a folded dipole? It provides a good impedance match to coaxial cable when used as a yagi's driven element.

Print and use this plan view when building the 15 element yagi wi-fi antenna.

Continue reading the next page for step by step construction guidance as well as mounting and testing the yagi wifi antenna. It is not hard to build, and provides plenty of gain for long range wifi networking.

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