Tracking, telemetry and command (TT&C) systems are critical elements for the success of space-based systems. For small satellites, they are steadily demanding highly integrated on-board equipment with significant reductions in physical parameters, recurrent costs and delivery time. This calls for innovative design approaches for on-board processing capabilities, modulation schemes and coding techniques. The peculiarities of on-board such TT&C transponders are considered. Algorithms of signal processing and their implementation in hardware (HW) and software (SW) of digital signal processor are dealt with in this work. The attainable characteristics suggest and foster using such transponders in TT&C radio links for small satellites.