A rapid method is used to find the least‐damped root of the dispersion equation for electrostatic waves in a Maxwellian magnetoplasma, including the effects of field‐aligned drift; the low‐temperature and low‐drift approximations are avoided. Calculations are made of the potential created by an alternating point charge at a frequency less than both the plasma and the electron cyclotron frequencies, neglecting collisions, forced ion motion, and the contributions of higher‐order roots. A comparison of the numerical results with the approximate expressions previously published shows that the latter are inadequate for diagnostic purposes, i.e., for deducing electron density, temperature, and drift velocity from measurements of the potential.