How do you design and construct a Yagi Uda antenna?

Question

I need dimensions and materials... Thanks...

Answer 1

The Yagi-Uda Antenna consists of a minimum of 3 elements, though 6 elements tend to be an optimum configuration.

One of the elements is called the "driven" element. One of the elements is called the "reflector" and the rest are called the "directors".

The reason why the reflector is such is wrapped up in transmission line theory. In a nutshell, the reflector is slightly longer than lambda/2 and it acts as an inductor and thereby acts as a reflector.

The directors are slightly shorter than lambda/2, acting as a capacitor and hence directs the wave.

Since the design is dependent on the wavelength of the RF wave you want to transmit, it is hard to give you dimensions. For a 6 element antenna, the overall length is ~1.5 lambda and the largest width is slightly larger than lambda/2. As an example, to transmit a 300 MHz wave, the length is ~1.5 meters and the width is slightly larger than .5 meters

As to materials, I've used hollow aluminum tubes for lightness, to make the elements.

Source(s):
Antennas by John Kraus, Second Edition, ISBN 0-07-035422-7

Answer 2

The design of this type of antenna is 100 per cent empirical. There are charts based on adjusting various spacing and length parameters which can be scaled to the operating frequency you need. Ham radio operators have been pretty successful at home brew construction on frequencies from 50 MHz to 1 GHz. Outside of that range the mechanical requirements become difficult. This is a narrow band antenna, for example it will only work properly for 1 television channel at VHF and a couple of channels at UHF. The natural feed impedence for this antenna type varies radically based on spacing and can be quite low and reactive making match to transmission line difficult. Information on suggested design and construction details are in antenna books published by ARRL.org