Radar System Engineering

298 ANTENNAS, SCANNERS, AND STABILIZATION [SEC.9.15
bend EE near the aperture has no optical effect and was introduced for
the sake of compactness. A plastic closure prevents moisture from
entering the horn at the edge BB. Accurate wood-working makes possible
the use of plywood construction which is preferable to aluminum in
weight and ease of manufacture.
The drive motor runs at 1725 rpm and is comected by a 7-to-1 gear
reduction to run the rotor about 4 rps. The azimuth data transmitter
is a capacitive voltage divider connected to a high-frequency oscillator.
*-75
c
,
~ D D
(b)
c
(a)
E
D
D
(c)
FIG. 9,26.—Successivesteps imagined in folding the Schwarzschildhorn.
The voltage developed across one of the condensers is detected and
applied to the indicator. This condenser is of the variable rotary type
and is driven at 16 rps, i.e., one revolution per scan.
The antenna is mounted on the vertical axis of the mount used for
the SCR-584 antenna, with certain alterations.
Approximately 100 plywood antennas were constructed during the
war. The production models that saw service showed no deterioration
over a period of one year.
9“15. SCI Height Finder.-This antenna is intended for use in rapid
coverage height-finding. 1 It is one of a pair of antennas (Fig. 9.28)
mounted on the same pedestal and rotating together in azimuth at 4
rpm. The other antenna is used for long-range search and azimuth
I C. V. Robinson, “ Tbe SCI Rapid Scan Heigh&6nding Antenna,” RL
No. 6S8
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