2. SA3R-20 Substitution Conclusion Substitution is feasible only under limited conditions and requires strict evaluation. While Fairview Microwave's SA3R-20 matches the original part in attenuation, power rating, and interface, a critical deviation exists in its frequency range—it only supports DC-3GHz, significantly lower than the original's 18GHz. This device is suitable solely for low-frequency applications below 3GHz (e.g., UHF, part of S-band). If deployed in circuits operating at higher frequencies (such as C, X, or Ku bands), its performance in attenuation accuracy, VSWR, and other parameters will degrade substantially or even fail, potentially leading to signal distortion or system performance degradation. Substitution should only be considered if the operating frequency is confirmed never to exceed 3GHz.