The need for charging on IoT nodes is essential for the sustainability of a wireless sensor network system. Therefore, one way is used, namely wireless power transfer, that can reach nodes in hard-to-reach areas. This research was conducted on the power conversion efficiency of a wireless power transfer system using amplitude modulation transmission with varying modulating signals. This study uses sinusoidal, sawtooth, square, and triangle waveforms as modulating signals. Simulations and measurements are carried out using an SDR programmed to be a transmitter as a wireless power transfer source and received at the other end using a rectenna system. The measures include the parameters of the received RF power (Pin RF) and the DC output voltage (VoutDC) to obtain the efficiency of RF to DC power conversion (nRF-DC). From the measurement results of these three parameters, the sinusoidal waveform is the most efficient waveform based on experiments with an efficiency value of 66% at 40 cm and a relatively constant when on the far field region (more than 60 cm) with an efficiency of about 1%.