Observation of the Earth from aerial and spaceborne platforms using synthetic aperture radar (SAR) has provided scientists and researchers with a deeper knowledge of the physical surface information of the planet. With the aim of launching our own SAR sensor into orbit for the purpose of remote sensing, we have a program to test our systems in an airborne platform. Prior to that, we need to first test all related on-board subsystems of SAR sensor on the ground. A semi-automated rail enabled ground-based SAR imaging test-bed was developed and is able to function carrying our L-band SAR systems. Part of the challenge in this project is the scale, as related L-band SAR system is relatively larger than systems of higher bands. The target and scan area covered in the ground measurement is also large, leading to a rail design that need to be extendable yet still mobile. This paper explains our system's radio frequency (RF) subsystem, which generates, transmits and receives the electromagnetic waves and also the rail-based Positioner Subsystem. In addition, the paper also shows the SAR system design specifications, how they are applied into the RF subsystem, and its implementation with the moving platform of the Positioner Subsystem in a field test.