This paper presents a compact model for LINC (linear amplification with non linear components) transmitters an their power combiners. The study focuses on the detrimental effect of the transmission line nonidealities. A mathematical description of the system that considers these nonidealities is proposed. The developed analytical expressions can be used to optimize, analyze and build pre-distortion algorithms for this family of transmitters. The efficiency and linearity are reexamined in light of the new analytical expressions of the model.