This work investigates vector modulators with respect to their applicability in agile beamsteering frontends. The turnover time, i.e. the time necessary for an amplitude or phase change, of two vector modulators is characterized. Both circuits offer high amplitude and phase control range within a wide bandwidth. They were designed in low-cost silicon processes and are already integrated with digital control circuitry, making them very attractive for commercial applications. In future traffic and industry applications, realtime requirements become more and more important. The necessary time for a 360° phase change was determined to be 100 ns and 5.6 μs for polar and cartesian vector modulator, respectively, whereas the time for a 40 dB amplitude change could be measured to 5.6 μs for both. To our knowledge, this is the first investigation on the transient behavior of vector modulators.