2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/17538Measurements of the temperature dependence of the surface resistance at 3 GHz of 100 micron size grains of MgB_2 separated powder are presented and discussed. The microwave surface resistance data is compared to experimental results of Nb, Bi_2Sr_2CaCu_2O_{8+δ} (BSCCO) and theoretical predictions of s-wave weak coupling electron-phonon theory (BCS).4 pages, 2 figures; accepted in SUSTSuperconductivitytext