The present disclosure generally relates to a rail warning system using wireless portable transmitters/receivers. The rail warning system uses a chirp spread spectrum modulation scheme, and alerts personnel in work zones on or near train tracks as well as optionally, on track equipment and train operators, of approaching trains or on track equipment. Portable wayside devices may also be positioned on the rail web, optionally magnetically, to alert work personnel, allowing for secure placement but also portability to other locations on the same track or adjacent tracks.