Fig. 7
AM-2 Transmitter
In addition to radio direction finding with the SCR658 and beacon transmission with radio compass, several other methods of balloon positioning were evaluated. Radar positioning was successful only if a target was attached to the balloon train. Generally, the ranges possible with radar are not as great as those possible by radio direction finding. For direction finding on the low frequency AM transmitter some value was found in use of loop antennae. Accuracy of this method is between .5 and 2 degrees and is generally hindered by sky wave reflection.
A pulse time modulated transponder beacon at high frequencies was found to be advantageous for obtaining accurate slant range to the balloon. Preliminary investigation of use of Doppler effect for positioning indicated that this method is not feasible due to difficulty in measuring the low frequency differences involved.