Time‐resolved free‐space microwave measurements are used to study the loss mechanisms in the afterglow of an intense He discharge between 100 and 1000 &mgr;. The method of evaluation is developed in detail and the results of the measurements and their accuracy are given. Some of the problems and limitations of the microwave method are discussed; in particular, plots of the field pattern between the horns are presented indicating that a reasonable interpretation in terms of an integrated path length is possible.