What is the radiation pattern of a dipole antenna in free space in a plane containing the conductor?

A half-wave dipole antenna in free space radiates energy broadside (at right angles) to the wire. If you look at the radiation pattern in the plane that contains the wire, it forms a shape with two main lobes that looks like a figure-eight. The strongest signals are emitted perpendicular to the antenna wire, while virtually no signal is radiated straight off the ends of the wire. This means if your dipole wire runs horizontally north-to-south, your best signal goes east and west. A perfectly circular pattern would only be seen if you were looking directly down the axis of the wire (the H-plane), not in the plane containing the conductor itself.