Abstract :
The accuracy of C.W. navigational aids in this frequency band depends fundamentally on the phase stability of the received signals, which in turn is determined by skywave effects. The r.m.s. phase errors depend on the relative amplitude of skywave and groundwave, and a method is given for assessing the phase errors in Northern Europe at any given time and range from the transmitter. For the sake of simplicity a number of approximations are made and the resulting limitations are discussed. The predicted and observed errors on the Decca Navigator Chains in England and Denmark are compared, and it is concluded that the method gives sufficiently accurate results for most practical purposes. Some comments are added on the variations of errors with height.
