A frequency-modulation, continuous-wave HF ionospheric sounder ('Chirp 1') was introduced in 1964. This equipment provided a considerable increase in system sensitivity over commonly used pulse sounders at a time-delay resolution of 10 microseconds. Experience with this equipment revealed a need for still greater time-delay resolution capability, plus easily selectable sweep frequency limits and rates, and an ability to sweep with either positive or negative slopes. In 1966, a second-generation equipment, 'Chirp 2', was developed. This report describes the differences between it and the 'Chirp 1' equipment. The salient characteristics of 'Chirp 2' are time-delay resolution of 1 microsecond or less, great flexibility in selection of sweep limits and sweep rates, and a choice of several sweep formats. The sweep phase discontinuities have been reduced to a level more than adequate for most ionospheric sounding work, but further reduction is needed in some applications. (Author).