A base station system comprising: at least three sectors, each sector of the at least three sectors providing a wireless communications service over a range of azimuth angles in a service area, each sector of the at least three sectors comprising at least one base station radio unit of a plurality of base station radio units; and a plurality of antenna systems, each of the plurality of antenna systems associated with a respective base station radio unit of the plurality of base station radio units, each antenna system of the plurality of antenna systems comprising a plurality of linear antenna arrays, each linear antenna array of the plurality of linear antenna arrays comprising a plurality of radiating antenna elements arranged linearly in a vertical plane, the plurality of linear antenna arrays disposed adjacent to each other in a horizontal plane, wherein each of the plurality of base station radio units is configured for operation in a particular band of radio spectrum and for applying precoding weights for beamforming signals via a respective antenna system of the plurality of antenna systems; in at least one antenna system of the plurality of antenna systems, at least one set of linear antenna arrays (411, 412) of the plurality of linear antenna arrays for an operating frequency associated with one of the plurality of base station radio units has an array separation distance of substantially 1.6+1.1n wavelengths apart at the operating frequency, where n is zero, 1 or 2; wherein the array separation distance minimizes radio frequency power radiated by grating lobes at angles which fall into service areas of sectors adjacent to a sector of the at least three sectors associated with the at least one antenna system, the grating being caused by the precoding weights of the one of the plurality of base station radio units when serving traffic within the sector associated with the at least one antenna system. at least three sectors, each sector of the at least three sectors providing a wireless communications service over a range of azimuth angles in a service area, each sector of the at least three sectors comprising at least one base station radio unit of a plurality of base station radio units; and a plurality of antenna systems, each of the plurality of antenna systems associated with a respective base station radio unit of the plurality of base station radio units, each antenna system of the plurality of antenna systems comprising a plurality of linear antenna arrays, each linear antenna array of the plurality of linear antenna arrays comprising a plurality of radiating antenna elements arranged linearly in a vertical plane, the plurality of linear antenna arrays disposed adjacent to each other in a horizontal plane, wherein each of the plurality of base station radio units is configured for operation in a particular band of radio spectrum and for applying precoding weights for beamforming signals via a respective antenna system of the plurality of antenna systems; in at least one antenna system of the plurality of antenna systems, at least one set of linear antenna arrays (411, 412) of the plurality of linear antenna arrays for an operating frequency associated with one of the plurality of base station radio units has an array separation distance of substantially 1.6+1.1n wavelengths apart at the operating frequency, where n is zero, 1 or 2; wherein the array separation distance minimizes radio frequency power radiated by grating lobes at angles which fall into service areas of sectors adjacent to a sector of the at least three sectors associated with the at least one antenna system, the grating being caused by the precoding weights of the one of the plurality of base station radio units when serving traffic within the sector associated with the at least one antenna system.