Antenna Theory - Inverted V-Antenna

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In the previous chapter, we have studied V-antenna. Its operating frequency is limited. This can be modified by using another antenna, which is a non-resonant antenna or a travelling wave antenna. A travelling wave antenna produces no standing wave, as discussed previously.

Frequency Range

The frequency range of operation of an inverted vee antenna (or V-antenna) is around 3 to 30 MHz. This antenna works in high frequency range.

Construction & Working of Inverted V-Antenna

A travelling wave antenna, used in high-frequency band is an inverted V-antenna. This inverted V-antenna is easily installed on a non-conducting mast.

Take a look at the following image. It shows an inverted V-antenna mounted on a roof top.

The maximum radiation for an inverted V-antenna is at its center. It is similar to a halfwave dipole antenna. The antenna is placed in the shape of an inverted V, with its two transmission lines or legs bent towards the ground making 120° or 90° angle between them. The center of the antenna should not be higher than λ/4.

The angle made by one of the legs with the axis of the antenna, is known as the tilt angle and is denoted by θ.

Radiation Pattern

The radiation pattern of inverted V-antenna is uni-directional pattern, as no standing waves are formed here. It can be clearly understood by the radiation pattern shown below.

The figure illustrates the radiation pattern of an inverted V-antenna. Primary radiated field is shown along with the fields when the tilt angles are 120˚ and 90˚ in the figure given above. The gain and directivity are improved by having an array of antennas.

Advantages

The following are the advantages of inverted V-antenna −

• Occupies less horizontal place

• No standing waves are formed

• High gain

Disadvantages

The following are the disadvantages of inverted V-antenna −

• It has considerable undesired minor lobes

• Minor lobes create horizontally polarized waves

Applications

The following are the applications of inverted V-antenna −

• Used in tuned circuit applications

• Used in radio communications

• Used in commercial applications

After the V-antenna and inverted V-antenna, another important long wire antenna is the Rhombic antenna. It is a combination of two V-antennas. This is discussed in the next chapter.