The protective device (limiter) at the receiver input is an important component, as it ensures the safety of the receiver operation in conditions of receiving powerful signals. The results of an experimental study of a protective device in the 1-4 GHz band are presented. It is shown that the minimum bandwidth losses at a low power level do not exceed 0.63 dB, the maximum bandwidth losses are 1.23 dB. At an input power of 25 dBm, the protective device operates in a non-linear mode, therefore it creates harmonics of the input frequency. The experimental amplitudefrequency response (AFC) of the protective device, as well as amplitude characteristics at three frequencies are presented. The experiment to remove the frequency response was carried out on a vector analyzer of circuits. The experiment to remove the amplitude characteristics was carried out using a standard signal generator and a spectrum analyzer at three frequencies: 1 GHz; 2 GHz; 4 GHz. Structurally, the protective device is a polycor substrate on which all elements except connectors are placed. The substrate is placed in a frame-type housing and closed with two sealed lids. Type III sockets according to GOST13317- 89 are used as connectors. A schematic diagram and a brief description of the design are given. The following main parameters have been achieved: losses do not exceed 1.23 dB in the operating frequency range from 1 to 4 GHz, the output signal power at a high input power level (f = 1 GHz; Rvh = 25 dBm) does not exceed 12 dBm. The protective device is recommended to be used in the input circuits of communication receivers, navigation, radar and electronic warfare
