  Exact results for the thermodynamic properties of ensembles of magnetic
impurities with randomly distributed host-impurity couplings in the quantum
antiferromagnetic Heisenberg model are presented. Exact calculations are done
for arbitrary values of temperature and external magnetic field. We have shown
that for strong disorder the quenching of the impurity moments is absent. For
weak disorder the screening persists, but with the critical non-Fermi-liquid
behaviors of the magnetic susceptibility and specific heat. A comparison with
the disordered Kondo effect experiments in dirty metallic alloys is performed.
