English: A collinear folded dipole antenna on a communication tower on Lake Mountain, Utah, USA. It consists of 4 vertical folded dipole antennas in a line, fed in phase. It is an omnidirectional antenna, radiating equal power in all horizontal directions. The advantage of using 4 antennas is that the horizontal gain is increased; more of the radio power is radiated in horizontal directions and less up into the sky and down toward the earth where it is wasted. Four collinear half wave dipoles have a gain of 6 dB over a single dipole's gain of 2.15 dBi or a total of 8.15 dBi. Collinear dipole arrays like this are often used as the base station antennas for dispatchers for radio-equipped mobile services such as police, fire, ambulance, taxi, and delivery services.