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When we talk about hf antennas for ham radio, Inverted V also known as inverted vee antenna appears to be the most favoured rf antenna for all ham radio enthusiasts.
While a number of antenna manufacturers provide hf antennas, an inverted vee antenna is easy to construct on your own and gives good performance when you are faced with space and other constraints to put up long wire antenna, dipole antenna or quad antennas.
An inverted vee antenna is a modified dipole antenna supported in the center with the ends lower than the center. Viewed from the side, it looks like the English letter "V" turned upside down, hence the name. Inverted vee antennas are commonly used by many ham radio stations, and aboard ships and sailing vessels which require better HF performance than available with a short whip antenna or other similar antennas.
Typically, the inverted vee antenna requires only a single, tall support at the center either in shape of bamboo pole, or metallic mast and even a good tall tree in your backyard, and the ends can be insulated and secured to anchors at or near ground level. This simplified arrangement has several advantages, including a shorter ground distance between the ends. For example, a dipole antenna for the 80 meter band requires a ground length of about 140 feet (43 m) from end to end. An inverted vee with a 40-foot (12 m) apex elevation requires only 115 feet (35 m). For ham radio amateurs living on limited plot size or small parcels of property, such space savings can make it possible to use the lower frequency amateur ham bands.
In theory, the gain of an inverted vee is similar to that of a dipole at the same elevation because most of the radiation is from the high-current portion of the antenna, which is near the center. Since the center of both antennas are the same height, there is little difference in performance. Antenna modeling software bears this out for free-space models, predicting maximum gain of 2.15 dBi for the dipole and 1.9 dBi for the inverted vee.
However, in practice, ground proximity and ground conductivity as well as end effects reduce the efficiency of the inverted vee considerably compared to the dipole: In the 40-foot example above, considering a useful take-off angle of 40 degrees above the horizon, the inverted vee produces a maximum gain of 1 dBi in a circular pattern, whereas the d
ipole produces an oval pattern ranging from 6 dBi toward the sides down to 1.2 dBi toward the ends.
Elevating the antennas higher above ground somewhat resolves the disparity, but considering the practical, legal and financial limits which influence most antenna installations, the inverted vee will be observably inferior in performance to a dipole by 1 to 2 S-units. However, if space is limited, an inverted vee may permit operation on frequencies that would not be possible with a full-sized dipole.
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