What is the approximate feed point impedance at the center of a two-wire half-wave folded dipole antenna?

A standard half-wave center-fed dipole in free space has a feed point impedance of approximately 72 ohms. When a second, parallel wire is added and connected at the ends to form a two-wire folded dipole, the current at the feed point is halved for the same amount of power. Because impedance is inversely proportional to the square of the current (Z = P / I^2), halving the current increases the feed point impedance by a factor of four. Four times 72 ohms is 288 ohms, which is widely approximated in practice as 300 ohms. This roughly 300-ohm impedance is highly convenient for operators because it provides a near-perfect match to standard 300-ohm twin-lead transmission line. Distractors like 50 or 72 ohms represent standard dipoles, while 450 ohms is associated with wide ladder line.