In this paper, we present a prototype test-bed for radio-frequency (RF) wireless power transfer (WPT) comprising a software-defined radio (SDR) transmitter and an energy harvesting receiver with a diode-based rectifier. The test-bed allows us to study the end-to-end efficiency of RF WPT when employing different co-phased multisine waveforms. In particular, we analyze the clipping and non-linear behaviours of the transmitter by experimentally evaluating how they affect the performance of waveforms. The experimental results indicate that transmitting impulse-like signals is actually not optimal for RF WPT in practice despite they would be ideal in terms of rectifier efficiency. Instead, the results highlight the superior performance of single-tone signals over co-phased multisines in terms of both end-to-end WPT efficiency and spectral purity.