What is the approximate impedance of a dipole that is 01 x w

What is the approximate impedance of a dipole that is (0.1 x wavelength)? That is (0.1 x wavelength) aboveground?

Solution

At 0.1 wavelength above the ground, the impedance of a horizontally polarized dipole antenna will be closer to 20 ohms, rather than the 72 ohms expected at the optimum height.

For example, an 80 meter dipole needs to be about 50 feet above the ground and away from other objects for the best results, and 75 ohms transmission line cable would be used. If a 50 ohms cable is desired, the antenna height could be more like 35 feet above the ground.