The design of coil/core transducers is important for maximizing the power density of inductive energy receivers for both inductive energy harvesting and power transfer. In this work, we present a study of core and coil performance, based on a simulated flux distribution corresponding to aircraft applications. The use of funnel-shaped soft magnetic cores boosts magnetic flux density by flux concentration and allows the use of a smaller diameter coil. This reduces the transducer mass as well as the coil resistance (RCOIL), thereby increasing the available power density. Analysis and simulation shows a fifty-fold power density increase from moderate funneling and another two-fold increase by coil size optimization. Results are compared with experimental measurements which demonstrate a 31 μW/g power density from alternating environmental magnetic fields in the 10 μT/360 Hz range.