H.F. Bearing Variations on an Adcock Direction-Finder

Measurements on a number of transmitters at ranges from 1000 to 5000 km show that the variance of snap bearings within a period of half an hour is of the order of 10deg2. To reduce this variance by a factor of ten, time averaging over about 5 min is required when the bearings are taken at 10 sec intervals. Bearing changes from hour to hour and from day to day have a variance of about 1 deg2 and thus set a limit to the error reduction obtainable by averaging over a halfhour period. The results are consistent with previously published estimates of bearing variances.