Abstract: The data transmitting and collecting hardware terminal of the automatic scanning frequency HF channel oblique sounding system (ASFHFCOSS) was designed based on the time synchronization means of global position system and the frequency synchronization technique of phaselocked loop. The terminal was implemented by making use of digital signal processor, complex programmable logic device, etc. The ASFHFCOSS hardware consists of the terminal related above and an HF transmitterreceiver, together with a computer. The software of the system was developed. The time synchronization error and the frequency synchronization error of the system are nearly zero, which make the high precise sounding of HF channel with a low transmitting power of tens of watts be possible. The digital signal processing procedure of the system was analyzed. Further, the HF channel experiments between Wuhan and Shangqiu were done in scanning frequency mode. The analyses of the data obtained were made, which show that the results from the sounding using ASFHFCOSS are capable of providing the basic information of HF channel properties.