This paper describes instrumentation for automatically measuring the phase and amplitude of randomly fluctuating pulsed radio signals reflected by the ionosphere. The phase detecting system is based on the null principle of servo‐mechanics, wherein the phase difference between transmitted and received signals is considered as an error to be annulled. The equipment is designed for pulsed operation at a carrier frequency of 60 kc, pulse width of 100 &mgr;sec, and a repetition rate of 12 pulses/sec. Amplitude and phase data are presented on a dual channel pen recorder.