This research evaluates the performance degradation of information channels in multifunction radar due to electronic countermeasures (standoff jamming) on main loop of radar antenna .This evaluation is performed by using the signal to noise ratio( SNR ) and the probability of detection parameters with and without jamming. Improvement of radar performance is proposed by using the following (ECCM) techniques :Constant False Alarm Rate( CFAR), Pulse compression (pc) , frequency agility (FA), Frequency Diversity(FD),Logarithmic Reception , and Automatic Gain Control(AGC). In this research MATLAB, software environment is used that has advanced mathematical tools, and graphical interactive ability.