The paper proposes a method of protection of the receiving paths of radio engineering and telecommunication systems of the ultra-high frequency range from the influence of powerful energy radiation on the basis of creating preliminary ionisation in the input circuits of the receiving path by using radioisotope-type ionisation sources. Recommendations for increasing the degree of protection of the input circuits of the receiving paths of on-board radio and telecommunication systems have been developed, which consist in the choice of a radioisotope source taking into account the required reflection of electromagnetic waves (0.1...10 Ci), as well as the need to ensure safe operation of equipment. As a radioisotope source, it is recommended to use materials with a half-life not less than the lifetime of onboard radio and telecommunication systems and that are clean sources of α-particles: Ro-210 (half-life - 138 days), Ru-238 (half-life - 86 years). To determine the value of the breakdown field strength, it is proposed to use the criterion of breakdown in gas discharge plasma, which takes into account the duration of the pulsed energy impact. An assessment of the effectiveness of the recommendations demonstrates the possibility of increasing the degree of protection of the input circuits of the receiving paths of on-board radio and telecommunication systems by a factor of ten.