Seasonal Variations in Direction of Arrival

Abstract

It is obvious from fig. 8.3 that the scatter of the received bearing directions is very large, especially during the time periods 0300 to 0900 and 1500 to 2100 GMT. Nevertheless, it is possible that some limits to this variation could be indicated by an investigation of the average behaviour over a long period. Such a series of results is presented in figs. 10.1, 10.2, 10.3 and 10.4. These figures show the relative number of times in particular bearing was received during the years 1953–1957. As many measurements as possible at any frequency within the range 12–21 MHz were made. The main factor limiting the number of results obtained was the cost of such a concentrated programme. The four sets of results correspond to the same four time-periods that appeared to show the different types of behaviour indicated in fig. 8.3. All the results shown in figs. 10.1 – 10.4 have been gathered together and included in the plots of bearing angle vs month of the year shown in figs. 10.5 – 10.8.