The proposed magnetic field energy harvester (MFEH) has two secondary coils, the original one to harvest energy from the primary powerline, and the additional one to desaturate the magnetic core. When the magnetic core is saturated by the magnetic field generated by the original coil, current starts to flow through the additional coil to desaturate the core. The desaturation controller is composed of a current sensor and a microcontroller unit (MCU) with associated switches. Experimental results show that the proposed circuit harvests 42.7 mW under powerline current of 25 A in rms. The circuit increases the amount of harvested power by 5.2 mW or 13.7 % through desaturation of the core.