The low-noise impedance converter Schwarzbeck VHIC 9260 with high-resistance, low-capacitance input impedance and 50 Ω output is used to measure the interference voltage at the base of vehicle antennas in the frequency range from 9 kHz to 120 MHz. Conventional measuring receivers or spectrum analyzers with 50 Ω input serve as display devices. A rod antenna or capacitive coupling pliers can be used as the signal source. The highly linear design allows the limit values to be measured precisely in accordance with CISPR 25. The HF connections are made with BNC sockets.