[en] A brief review of the development and application of techniques for measuring positron endpoint energies using intrinsic Ge detectors is given. The calculation of detector response functions using Monte Carlo methods is discussed. Multiple scattering, bremsstrahlung, photoelectron escape and interference from annihilation radiations are considered. The techniques were tested using well known endpoints of the decays of ₂₇Si, ₅₈Cu and ₆₄Ga. Q-values were determined for mass-separated samples of ₇₇Rb and ₇₇Kr produced in heavy ion reactions