It is important to enable remote control of duty cycle of air hammers via external distributors meant to set impact frequency. A new general layout is developed for the air-driven impact impulse generator with smooth adjustment of impact frequency at constant energy in driving construction elements in soil. The experimental model of the machine is designed and tested. Based on the analysis of the impulse indicator diagrams of the machine duty cycle, the impact frequency is correlated with the piston choke cross-section for three configurations of the control unit. The impact frequency control limits are found.