This paper targets reduction of RF testing costs, focusing in particular on the generation of modulated stimuli for testing the reception chain of RF communication devices. It proposes an innovative low-cost solution that can be implemented on a standard digital Automated Test Equipment (ATE). The approach relies on the generation of a baseband digital signal with specific encoding, and the exploitation of one of its harmonic replicas as RF test stimulus. Spectral integrity of the signal around the targeted harmonic replica is ensured through a careful selection of the ATE sampling frequency. A generic methodology for practical implementation is presented and illustrated in this paper considering two popular digital modulation formats, namely Binary Phase-Shift Keying (BPSK) and Minimum-Shift Keying (MSK). Experimental validation is performed using a microcontroller unit (MCU) capable of operating at a sampling rate up to 500Mbps. Results show that despite the limited sampling capability of the equipment, test stimuli with the desired spectral characteristics in the 433MHz and 868MHz ISM bands can be generated, validating the proposed solution.