Although radiowave photoconductivity measurement was expected to be sensitive enough to detect the transient behavior not only of photoelectrons but also of positive holes in silver halide grains, it was not necessarily successful owing to the lack of its stability and reproducibility. In this investigation, we made a theoretical study and simulation of this measurement technique and developed a new apparatus for it, with significantly improved stability and reproducibility. The coefficient of variation of the photoconductivity of AgBr grains with positive holes as carriers by the new apparatus was 3.6%, while that by the old one was 33.8%. It was demonstrated that the new apparatus was sensitive and reproducible enough to measure small changes in photoconductivity of silver halide grains with positive holes as carriers. These changes were undetectable by the previous one.