We propose an original technique for the HF radar estimation of the main sea state parameters by exploiting the amplitude modulation of the radar signal time series. While the classical method for ocean wave measurement is based on the second-order ocean Doppler spectrum, this alternative approach uses the slow amplitude modulation of the Bragg wave in the radar signal. Using a nearby buoy and the WWIII model as ground truth, we apply this method to an annual set of HF radar data in the vicinity of Toulon (Mediterranean coast of France) and compare it with \col{the classical formulas proposed by Barrick (1977) to derive the main wave parameters from the Doppler spectrum. Although the modulation approach is physically attractive and easier to implement, we find that the Doppler spectrum-based method is far superior at this stage in calculating the significant wave height and the peak wave frequency, even at long range.