For mast radiators the earth under the mast is part of the antenna; the current fed to the mast passes through the air into the ground under the antenna as displacement current (electric field). The ground also serves as a ground plane to reflect the radio waves. The antenna is fed power between the bottom of the mast and ground so it requires a grounding (Earthing) system under the antenna to make contact with the soil to collect the return current. One side of the feedline from the helix house is attached to the mast, and the other side to the ground system. The ground system is in series with the antenna and carries the full antenna current, so for efficiency its resistance must be kept low, under 2 ohms, so it consists of a network of cables buried in the earth. Since for an omnidirectional antenna the Earth currents travel radially toward the ground point from all directions, the grounding system usually consists of a radial pattern of buried cables extending outward from the base of the mast in all directions, connected together to the ground lead at a terminal next to the base.