TheCodeBreakers
exercises.
But cryptanalysis was only part of the unit's task. The great majority
of its 100 officers and men worked on two other aspects of radio
intelligence—direction-finding and traffic analysis.
Direction-finding locates radio transmitters. Since radio signals are
heard best when the receiver points at the transmitter, sensitive
antennas can find the direction from which a signal is coming by
swinging until they hear it at its loudest. If two direction-finders take
bearings like that on a signal and a control center draws the lines of
direction on a map, the point at which they cross marks the position of
the transmitter. Such a fix can tell quite precisely where, for example, a
ship is operating. Successive fixes can plot its course and speed.
To exploit this source of information, the Navy in 1937 established the
Mid-Pacific Strategic Direction-Finder Net. By 1941, high-frequency
annaabi.ee 
