The invention relates to an antenna diversity arrangement and a radio base station in a frequency divided mobile cellular system with sectorized cells. Space diversity or polarization diversity is provided by providing at least two branches. In accordance with the invention an operator frequency band is divided into a plurality of bands for transmitting and receiving. All sectors are branch wise combined in a respective tower mounted amplifier. TX signals within the TX bands belonging to a TMA are diplexed and simultaneously transmitted on the sectors. RF signals received on one branch of a sector are combined with RF signals received on the corresponding sector in the other branches. The RX signals so combined are fed to the radio base station on a single feeder together with the TX signals fed in the opposite direction from transceivers of the base station to the same TMA. A sector may be assigned two or more TX frequencies. Frequency hopping within each TX band may optionally be provided (synth hopping). If two or more TX frequencies are assigned to a sector synth hopping may be combined with frequency hopping between the TX bands assigned to the sector in the A branch as well as the TX bands assigned to the corresponding sector in the B branch.