Aiming at the physical layer communication technology of civil aviation VHF data link, based on the radio frequency front-end HackRF One and software GNU Radio, a low-cost reconfigurable software radio simulation platform is built, and the text transmission for digital signals of civil aircraft VHF data link mode 4 (VDL M4) is implemented in the programming environment. The implementation scheme of communication modules such as GFSK modulation and demodulation is expounded, and a new symbol synchronization module is designed according to the signal synchronization problem existing in GNURadio. Experiments show that the VDL M4 transceiver meets the design requirements specified by ICAO documents and can better transmit text data.