Yagi uda antenna

The practical gain of a Yagi is 6 to 20 dBi, depending on the number of elements. The Yagi—Uda array in its basic form has very narrow bandwidth, 2—3 percent of the centre frequency. The "reflector" and "director" elements increase the strength and narrow the antenna beam in the direction in front of the antenna.

This so-called trap has the effect of truncating the element at the higher frequency band, making it approximately a half wavelength in length. However these elements are not driven as such but receive their energy from the field created by the driven element, so we will find almost the opposite to be true.

The center rod like structure on which the elements are mounted is called as boom. The elements in front of the dipole are called director. The antenna propagates electromagnetic field energy in the direction running from the driven element toward the director sand is most sensitive to incoming electromagnetic field energy in this same direction.

characteristics of yagi uda antenna

The director elements those to the right of the feed in Figure 1 will be shorter than resonant, making them capacitive, so that the current leads the voltage. As alluded to in the previous paragraph, the lengths of the directors are typically less than the resonant length, which encourages wave propagation in the direction of the directors.

Isotropic antenna radiates uniformly in all direction. This leads to the array being designated as a travelling wave antenna.

Yagi uda antenna diy

Uda did not speak English, but his student did. The reflector is the lengthy element, which is at the end of the structure. Just considering two such elements we can write the voltage at each feedpoint in terms of the currents using the mutual impedances Zij: V. Gain versus separation for 2-element Yagi antenna. In fact, that would be the case were we to construct a phased array with rather closely spaced elements all driven by voltages in phase, as we posited. Similarly, the gain for this Yagi antenna can be plotted as a function of director spacings, or as a function of the number of directors used. Using a second set of traps, a "triband" antenna can be resonant at three different bands. The case of a Yagi—Uda array using just a driven element and a director is illustrated in the accompanying diagram taking all of these effects into account.

Gain versus separation for 2-element Yagi antenna.

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Yagi Uda Anteena Designing Steps