Definition

Yagi antenna (Yagi-Uda array)

A Yagi antenna, also known as a Yagi-Uda array or simply a Yagi, is a directional antenna commonly used in communications when a frequency is above 10 MHz. This type of antenna is popular among Amateur Radio and Citizens Band radio operators. It is used at some surface installations in satellite communications systems.

A basic Yagi consists of two or three straight elements, each measuring approximately1/2 electrical wavelengths. The antenna can be balanced or unbalanced. The Yagi is inherently a balanced antenna, but it can be fed with coaxial cable and a device called a balunat the point where the feed line joins the driven element.

The driven element of a Yagi is the equivalent of a center-fed, half-wave dipole antenna. Parallel to the driven element, and approximately 0.2 to 0.5 wavelength on either side of it, are straight rods or wires called reflectors and directors. A reflector is placed behind the driven element and is slightly longer than 1/2 wavelength; a director is placed in front of the driven element and is slightly shorter than 1/2 wavelength. A typical Yagi has one reflector and one or more directors. The antenna propagates electromagnetic field energy in the direction running from the driven element toward the director(s), and is most sensitive to incoming electromagnetic field energy in this same direction.

The Yagi antenna not only has a unidirectional radiation and response pattern, but it concentrates the radiation and response. The more directors a Yagi has, the greater the so-called forward gain. As more directors are added to a Yagi, it becomes longer. Some Yagi antennas have as many as 10 or even 12 directors in addition to the driven element and one reflector. Long Yagis are rarely used below 50 MHz, because at these frequencies the structure becomes physically unwieldy.

This was last updated in April 2005
Posted by: Margaret Rouse

Email Alerts

Register now to receive SearchMobileComputing.com-related news, tips and more, delivered to your inbox.
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

More News and Tutorials

  • Rugged mobile devices must be more than durable in harsh environments

    The durability of ruggedized mobile devices is only the first consideration for mobile managers with workers who take devices into hazardous environments. Connectivity, usability and portability are also important features.

  • Mobile phone beats out smartphone as device of choice

    Mobile phones edged out smartphones as the most commonly used devices in organizations, according to SearchMobileComputing.com's recent survey, which also found that many companies support any kind of devices brought in by users.

  • Mobile data services -- getting connected

    Mobile data computing continues to grow as more service providers offer services and at increasing speeds. Different ways to connect to the mobile data network are discussed in this tip by Paul DeBeasi.

Do you have something to add to this definition? Let us know.

Send your comments to techterms@whatis.com

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: