A new low-cost reconfigurable software-defined radio (SDR) platform for high-frequency (HF) applications is presented in this article. The platform can work in the entire HF band (3-30 MHz), with bandwidths up to 36 kHz. We present the preliminary results working in a near vertical incidence skywave (NVIS) communication, where only the frequency range 3-12 MHz is needed. The modem has been designed so that the modulations to be used, time frames, and scheduling can be completely reprogrammable in both narrow-band and wide-band modes. This is a strong advantage, because tests can be redesigned and reprogrammed to evaluate channel performance, which is not only important for research purposes but also for its final application in emergency communications in the NVIS propagation case of study. The transmission can be adapted to the best propagation frequency at every moment by means of a previous sounding analysis.