8.3.1 All radar installations shall comply with the following minimum
requirements.
8.3.2 Range performance
The operational requirement under normal propagation conditions, when
the radar antenna is mounted at a height of 15 metres above sea level,
is that the equipment shall in the absence of clutter give a clear
indication of:
- Coastlines
At 20 nautical miles when the ground rises to 60 metres.
At 7 nautical miles when the ground rises to 6 metres.
- Surface Objects
At 7 nautical miles a ship of 5,000 tons gross tonnage, whatever
her aspect,
At 3 nautical miles a small vessel of 10 metres in length.
At 2 nautical miles an object such as a navigational buoy having
an effective echoing area of approximately 10 square metres.
8.3.3 Minimum Range
The surface objects specified in paragraph 8.3.2.2 shall be clearly
displayed from a minimum range of 50 metres up to a range of one
nautical mile, without changing the setting of controls other than the
range selector.
8.3.4 Display
8.3.4.1 The equipment shall without external magnification provide a
relative plan display in the head-up unstabilized mode with an effective
diameter of not less than:
- 180 millimetres (7 and 9 inch) on ships of 500 tons
gross tonnage and more but less than 1,600 tons gross tonnage;
- 250 millimetres (12 inch) on ships of 1,600 tons gross tonnage
and more but less than 10,000 tons gross tonnage;
- 340 millimetres (16 inch) in the case of one display and 250
millimetres in the case of the other on ships of 10,000 tons gross
tonnage and upwards.
8.3.4.2 The equipment shall provide one of the two following sets of
range scales of display:
- 1.5, 3, 6, 12 and 24 nautical miles and one range scale of not
less than 0.5 and not greater than 0.8 nautical miles; or
- 1, 2, 4, 8, 16 and 32 nautical miles.
8.3.4.3 Additional range scales may be provided.
8.3.4.4 The range scale displayed and the distance between range
rings shall be clearly indicated at all times.
8.3.5 Range measurement
8.3.5.1 Fixed electronic range rings shall be provided for range
measurements as follows:
- where range scales are provided in accordance with paragraph
8.3.4.2.1, on the range scale of between 0.5 and 0.8 nautical miles
at least two range rings shall be provided and on each of the other
range scales six range rings shall be provided; or
- where range scales are provided in accordance with paragraph
8.3.4.2.2, four range rings shall be provided on each of the range
scales.
8.3.5.2 A variable electronic range marker shall be provided with a
numeric readout of range.
8.3.5.3 The fixed range rings and the variable range marker shall
enable the range of an object to be measured with an error not exceeding
1.5 per cent of the maximum range of the scale in use, or 70 metres,
whichever is the greater.
8.3.5.4 It shall be possible to vary the brilliance of the fixed
range rings and the variable range marker and to remove them completely
from the display.
8.3.6 Heading Indicator
8.3.6.1 The heading of the ship shall be indicated by a line on the
display with a maximum error not greater than plus or minus 1 degree.
The thickness of the displayed heading line shall not be greater than
0.5 degrees.
8.3.6.2 Provision shall be made to switch off the heading indicator
by a device which cannot be left in the "heading marker off"
position.
8.3.7 Bearing Measurement
8.3.7.1 Provision shall be made to obtain quickly the bearing of any
object whose echo appears on the display.
8.3.7.2 The means provided for obtaining bearings shall enable the
bearing of a target whose echo appears at the edge of the display to be
measured with an accuracy of plus or minus 1 degree or better.
8.3.8 Discrimination
8.3.8.1 The equipment shall be capable of displaying as separate
indications on a range scale of 2 nautical miles or less, two small
similar targets at a range of between 50 per cent and 100 per cent of
the range scale in use, and on the same azimuth, separated by not more
than 50 metres in range.
8.3.8.2 The equipment shall be capable of displaying as separate
indications two small similar targets both situated at the same range
between 50 per cent and 100 per cent of the 1.5 or 2 mile range scales,
and separated by not more than 2.5 degrees in azimuth.
8.3.9 Roll or Pitch
The performance of the equipment shall be such that when the ship is
rolling or pitching up to plus or minus 10 degrees the range performance
requirements of paragraph 8.3.2 and 8.3.3 continue to be met.
8.3.10 Scan
The scan shall be clockwise, continuous and automatic through 360
degrees of azimuth. The scan rate shall be not less than 12 revolutions
per minute. The equipment shall operate satisfactorily in relative wind
speeds of up to 100 knots.
8.3.11 Azimuth stabilization
8.3.11.1 Means shall be provided to enable the display to be
stabilized in azimuth by a transmitting compass. The equipment shall be
provided with a compass input to enable it to be stabilized in azimuth.
The accuracy of alignment with the compass transmission shall be within
0.5 degrees with a compass rotation rate of 2 revolutions per minute.
8.3.11.2 The equipment shall operate satisfactorily in the
unstabilized mode when the compass control is inoperative.
8.3.12 Performance check
Means shall be available, while the equipment is used operationally,
to determine readily a significant drop in performance relative to a
calibration standard established at the time of installation, and to
check that the equipment is correctly tuned in the absence of targets.
8.3.13 Anti-clutter devices
Suitable means shall be provided for the suppression of unwanted
echoes from sea clutter, rain and other forms of precipitation, clouds
and sandstorms. It shall be possible to adjust manually and continuously
the anti-clutter controls. Anti-clutter controls shall be inoperative in
the fully anti-clockwise positions. In addition, automatic anti-clutter
controls may be provided; however, they must be capable of being
switched off.
8.3.14 Operation
8.3.14.1 The equipment shall be capable of being switched on and
operated from the display position.
8.3.14.2 Operational controls shall be accessible and easy to
identify and use. Where symbols are used they should comply with the symbols
for radar controls in paragraph 8.9 of this document.
8.3.14.3 After switching on from cold the equipment shall become
fully operational within 4 minutes.
8.3.14.4 A standby condition shall be provided from which the
equipment can be brought to an operational condition within 15 seconds.
8.3.15 Interference
8.3.15.1 After installation and adjustment on board, the bearing
accuracy as prescribed in these standards shall be maintained
without further adjustment irrespective of the movement of the ship in
the earth's magnetic field.
8.3.16 Sea or ground stabilization (true motion display)
8.3.16.1 Where sea or ground stabilization is provided the accuracy
and discrimination of the display shall be at least equivalent to that
required by these standards.
8.3.16.2 The motion of the trace origin shall not, except under
manual override conditions, continue to a point beyond 75 per cent of
the radius of the display. Automatic resetting may be provided.
8.3.17 Antenna system
8.3.17.1 The antenna system shall be installed in such a manner that
the design efficiency of the radar system is not substantially impaired.
8.3.18 Operation with radar beacons
8.3.18.1 All radars operating in the 3 centimetre band shall be
capable of operating in a horizontally polarized mode.
8.3.18.2 It shall be possible to switch off those signal processing
facilities which might prevent a radar beacon from being shown on the
radar display.