R&D Report 1986-13 : VHF-FM radio broadcasting: tests to compare horizontal, vertical and mixed polarisations. G.H. Taylor, D.S. Cox The BBC is re-engineering its VHF-FM radio networks from horizontal to mixed polarization. This Report describes tests carried out to monitor this change and which confirm the advantages of mixed polarization. Tests from the BBC transmitting station at Wenvoe to compare vertical and horizontal polarization are described. It is concluded that mixed polarization is the best choice for re-engineering the UK VHF-FM networks. For new network s the optimum polarization would be vertical, with the option of adding a horizontal component for areas where interference to fixed installations could be lessoned by the use of the additional directivity available with horizontally polarized receiving antennas.