In this paper, a power line data transmission link based on Software-Defined Radio (GNU Radio) for motor cable communication between an electrical motor and a frequency converter is developed and tested. The test environment includes a frequency converter, an electrical motor (2.2 kW), and a 90-meter-long motor power cable. Two differential phase shift keying (DPSK) modulations, DBPSK and DQPSK, are used and their performance is compared with and without forward error correction (FEC). Experiments prove that GNU Radio with USRP (Universal Software Radio Peripheral) is a competent platform to be used as a testing and developing power line communication applications.