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Tuesday, November 14, 1972
The SSR system operates by sending out an interrogation signal from
the ground radar to be received by the aircraft radar beacon, known as a
transponder.
The aircraft, in reply, transmits a series of pulses in a number of
combinations according to the information required on the ground.
The ground system receives the signals transmitted and automatically
decodes them.
Thus the ground controller knows not only the range and bearing of
the aircraft, which is supplemented with the help of the existing primary radars,
but also additional information on its identity and altitude.
A 1971 survey of 27 airlines operating scheduled services through
Hong Kong showed that at least 97 per cent of the aircraft flying in and out
during busy periods in the afternoon were equipped with these transponders.
The existing primary radars will have to be retained to provide
information on aircraft which either fail to respond to the ground radar, or
are not equipped with transponders.
New equipment to be installed will include interrogation and decoding
equipment, which will be located on Mount Parker, and processing equipment,
which will register information obtained by the new radar with the three existing
primary radars.
The cost and installation of this radar system is estimated to be around
$5.5 million.
In order to study the system in actual operation and to foresee any
problems that might arise, two officers from the Civil Aviation Department visited
a number of manufacturers in May this year, and made recommendations as to the
final choice of equipment.
It is expected that the new radar system will be operational by mid-1974.
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