Electromagnetic coils are used in a wide variety of engineering applications. The magnitude of current (and hence magnetic field strength) is inherently frequency-dependent; above the coil’s breakpoint frequency current reduces in proportion to frequency. This effect often limits the high-frequency performance of devices. A magnetically-coupled conducting loop (“shorted-turn”) may produce beneficial effects of reducing the primary coil’s electrical impedance at high frequencies. This shorted turn effect was modelled using linear transfer function analysis and shown to have close agreement to experimental frequency-response measurements. Parameter sensitivity analysis was conducted to identify the effect of individual shorted-turn variables on the frequency response of a primary coil. Experimental variation of shorted-turn parameters confirmed the theoretical analysis, with thicker-walled, lower-resistance loops providing a more pronounced modification of primary coil response. These results and analysis provide a framework to design shorted-turns within electrical devices to optimise high-frequency behaviour.