  We report systematic studies of AC magnetic susceptibility and transport
properties of Y(1-x)Ca(x)Ba2Cu3Oz bulk samples with 0\leq x\leq 0.4. Single
phase materials, reduction of carrier concentration and decrease of Tc to 85 K
were obtained at doping levels up to 20%. For Y0.7Ca0.3Ba2Cu3Oz sample the
improvement of grains boundary transport and screening capabilities has been
observed as a result of the optimal ratio between carrier concentration and
impurity phase BaCuO2 presence. The appearence of bulk pinning and nonlinear
effects starting at the highest temperature were detected also.
