High quality television services entail more complex systems and higher costs of prototyping, development and testing methods. The concept of Software-Defined Radio, which addresses flexibility and adaptability to new systems as they are researched, is an option to study the behavior of some technologies that will be used in future systems. This paper presents an overview of the new Advanced Television Systems Committee (ATSC) system, named ATSC 3.0. Finally, it proposes an implementation of ATSC 3.0 modulator using the GNU Radio Companion (GRC) software and validates the implementation transmitting and receiving the signal with a third party hardware and software.