Vector S-parameter measurements of the superconducting vortex flow transistor (VFT) are presented. The measurements were obtained for frequencies up to 100 MHz on VFTs that had a calculated transit-time cutoff frequency of 5 GHz. An equivalent circuit model that includes calculations of the VFT transresistance, input inductance, and feedthrough capacitance is derived from these measurements. The measurements are limited to an upper frequency of 100 MHz due to crosstalk in the low-impedance system.