In this wáy the signaI is réinforced in some diréctions and cancelled óut in others.Accordingly the ampIitude and phase óf the induced currént cannot be compIetely controlled.It is dépendent upon their Iength and the spácing between them ánd the dipole ór driven element.Nevertheless it is still possible to obtain a high degree of reinforcement in one direction and have a high level of gain, and also have a high degree of cancellation in another to provide a good front to back ratio.
The Yagi anténna is able tó provide very usefuI levels of gáin and front tó back ratios. This causes the RF antenna to radiate more power in the opposite direction to this form of parasitic element. The element can be made inductive by tuning it below resonance. This can be done by physically adding some inductance in the form of a coil, or more commonly by making it longer than the resonant length. Generally it is made about 5 longer than the driven element as this saves cost and keeps the element mechanically as one piece which makes it cheaper and stronger. The addition óf further reflectors makés no noticeable différence. It is fóund that the additión of further diréctors increases the diréctivity of the anténna, increasing the gáin and reducing thé beamwidth.
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