This study focuses on the application of orbital angular momentum (OAM) modes for enhancing radio communications. It is shown that OAM modes can enhance the spectral efficiency of line-of-sight links where there is limited or no diversity gain, and also increase physical layer security. Multiple-input multiple-output systems, in comparison, can struggle to give spectral efficiency improvements in line-of-sight links because they are not typically configured to exploit OAM modes. The concept of specifically using OAM modes shows great promise provided that several challenges are addressed. This study aims to clarify OAM in the context of applications to which it is well suited, such as high-capacity point-to-point links alongside transport infrastructure, within data centres, and between buildings.