Inverted-V Dipole Calculator

How the sloping geometry changes the dipole

An inverted-V is a half-wave dipole whose two arms slope downward from a single high centre support. The image shows the geometry clearly: the feedpoint is elevated while both ends descend toward lower supports. This arrangement is popular because it needs only one tall support and can fit where a straight horizontal dipole cannot. It is especially useful for portable stations, field deployments and small residential plots.

The calculator starts with the half-wave dipole relationship but the final impedance and resonant frequency are affected by the included angle and the height of the wire ends. A narrow included angle generally produces a different feedpoint impedance from a broad V. The proximity of the lower wire ends to the ground can also alter the electrical behaviour. For that reason, the calculated length should be treated as a starting dimension rather than an exact final cut length.

When building an inverted-V, keep the two arms as equal as practical and keep the centre support mechanically independent of the coax connector. Leave enough clearance around the sloping ends to prevent accidental contact with people, buildings and trees. The feedline should normally descend away from the feedpoint in a controlled route. If common-mode current is affecting tuning or causing RF on the outside of the coax, a suitable choke may help. Raise the antenna into its final geometry before tuning it. Trim both arms in small, equal increments and record the angle, height and final dimensions. The image is important to the page because the calculator's practical correction only makes sense when the user understands that the antenna is no longer a straight horizontal dipole.