In recent years, the limiting characteristics of detectors and mixers based on high-temperature superconducting Josephson junctions (JJs) have been actively studied. In the majority of works, an increase in sensitivity at low temperatures has been demonstrated, although a part of papers indicate the receiver's operation optimum at intermediate temperatures between the liquid nitrogen and helium temperatures. We report on a temperature dependence of the first Shapiro step amplitude for an external signal with frequencies of 72 GHz and 265 GHz acting on YBa2Cu3O7-δ Josephson grain boundary junction [1-3]. The observed non-monotonous behavior of the step height in the limit of low signal power is discussed. The step heights are in agreement with the calculations based on the resistively-capacitively shunted junction model and Bessel theory. The occurrence of the receiving optima is explained by the mutual influence of the varying critical current and the characteristic frequency. The maximum response to a 72 GHz signal has an optimum at 70 K, to a 265 GHz signal - 50 K. The obtained optima arise at certain JJ parameters: normal resistance RN, critical current IC(T), characteristic frequency ωC(T). For specific purposes and operation regions, it is possible to tune JJ parameters to operate in the optimal regime.