Radar System Engineering

208 THE GATHERING AND PRESENTATION OF RADAR DATA [~EC.614
helical scan. Alternatively, the antenna could be set to rotate uniformly
in azimuth, the elevation being manually controlled, or both azimuth and
elevation could be manually controlled. The performance at 10-cm
wavelength was more than adequate to give the 60,000-yd range desired
on single aircraft, and the convenience of having a common radar perform
both the search and the tracking functions is very great. Figure
FIG. 636,-LHTR
.
transmitter-receiver-power-supplyunit usedin AN/APG-15 and other
sets.
6.37 shows an “x-ray” view of the SCR-,584 with the antenna elevated into
operating position. For traveling, it is lowered within the trailer.
A conical scan is executed by the antenna of the SCR-584, the dipole
feed of the 6-ft paraboloid rotating rapidly about an axis which is that of
its mechanical, tbough not its electrical, symme try. For precision tracking,
the azimuth and elevation error signals derived from this conical scan
are used, not to give an indication of pointing error, but actually to drive
servomechanisms which ~osition the antenna mount. An error signal
in either coordinate will cause the antenna to move in the direction necessary
to reduce. the error. This so-called “automatic angle tracking” was