C.W. sounding and its use for control of h.f. (3-30MHZ) adaptive systems for data transmission

A theoretical analysis is presented in which the phase pertubations of the sounding signal due to ionospheric propagation are interpreted into a `phase-error¿ rate. An indication of how this may be used to assess the likely error rate associated with an information channel using that frequency is also given. The paper describes how the sounding technique will be used to control the time at which to change frequency, the best standby frequency and the degree of redundancy required to protect the information. The paper is a sequel to that presented by the authors at the IEE conference on signal-processing methods for radio-telephony, London, May 1970.