The gain of an antenna indicates the increase of its transmission energy. Gain is a result of transmission energy focused through the antenna in horizontal and/or vertical direction. A ball emitter emitting transmission energy uniformly in all directions has no antenna gain (0 dBi or 0 dBd). The ball emitter is a theoretical concept used for calculating antenna gain. Omnidirectional antennas radiate transmission energy horizontally in a 360° radius, while less than 360° on a vertical axis. This means for instance that the antenna item number 10926 has an antenna gain of 2,5 dB.