Comments on "The Measurement of Noise in Microwave Transmitters" [Letters]

In the recent paper, "The Measurement of Noise in Microwave Transmitters," J. R. Ashley et al. give a review of several methods for the measurement of AM and FM noise, respectively. The section, which deals with FM noise measurements at frequencies below 5 GHz, may be the source of erroneous conclusions, as will be pointed out in this comment.