The scaling of antenna-plasma momentum coupling in a Direct Wave-Drive Thruster (DWDT) was investigated analytically and experimentally in order to clarify the general thrust scaling in such an accelerator. The analytical model extends previous work by including the full dispersion relationship and predicts that thrust scales with the square of frequency and antenna current, (ωJa)2. Experimental validation was indirectly carried out using a Mach probe to measure the plasma velocity in the plume of the DWDT Experiment. The plume Mach number was measured for a constant configuration of the plasma source density and background magnetic field while varying the current and frequency of the accelerating antenna. The change in Mach number was observed to be a function of (ωJa)2 in agreement with our model’s prediction.