N.S. Klyba, A.V. Levsha, V.V. Pechurin, V.А. Shashlov

Modern radio monitoring facilities use digital wideband processing. This processing are executed after amplification of group radio signal. The group radio signal is combination of the narrow-band radio signals. Difference between levels of the signals activates intermodulation interference, when amplification is on. It distorts real signal situation and leads to reducing of overall performance of the radio monitoring facilities. For reducing intermodulation interference it is offered to use controlled attenuator before an amplifier. Reduction of a group radio signal level in n times leads to the same reduction of interference level and to reduction in n(q-1) times of intermodulation interference level, where q - the power of an intermodulation interference. For acknowledgement of theoretical premises practical experiments have been made. The results showed that a spectrum mean of a group radio signal decreases on 4 - 5 dB at optimal attenuation. It happens because of reduction of an intermodulation interference amount and lowering of their levels.