4.3.5 VOR
At ground level a circle of 230 metres radius from the site centre with a further slope at 2% (1:50) out to 900 metres radially from the site centre.
4.3.6 DME
The foregoing VOR constraints where co-located with a VOR otherwise a 2% (1:50) slope surface originating at the site ground level extending 300 metres radially.
4.3.7 Radar – 10 cm, 23 cm, 50 cm and SSR
4.3.7.1 The radar system shall be safeguarded with criteria which are derived from the following as a minimum: a) Operational Range. b) Base of Coverage. c) Operational Usage.
d) Equipment Manufacturer’s recommended clearances to prevent deterioration of the system’s performance.
4.3.7.2 The criteria for safeguarding should include the following for all radar systems: a) A Sterile Zone around the antenna to permit clean, uninterrupted beam formation; i) which should be precisely defined with respect to a clear reference point on the antenna system, ii) which should be derived from the vertical and horizontal beam patterns of the antenna type, iii) which should state both the vertical and horizontal extents of the Sterile Zone. b) A safeguarded slope should be defined around the system which shall assure the
system’s performance such that it continues to support the operational requirement; i) which should be precisely defined with respect to a clear reference point on the
antenna system, ii) which should define the gradient of the slope.
c) The criteria should also include consideration of the construction, shape, location, orientation and materials used in any application.
NOTE 1:Example of Sterile Zone criteria: 'The Sterile Zone is an area of z metres in radius centred on the rotation axis of the radar antenna. The zone extends y metres below the electrical centre of the antenna.'
NOTE 2:Example of slope criteria: 'The protected slope shall be 1 in a*, centred on a point on the rotation axis of the radar antenna that is b* metres below the lower edge of the antenna. The slope shall extend to a ground distance of c* metres from the rotation axis of the antenna.'
*a, b and c are numbers defined by the system characteristics.
4.3.7.3 For clarity, the safeguarded areas should be described diagrammatically as well as textually.
4.3.8 Surface Movement Radar The airport boundary from ground level.
4.3.9 VHF Direction Finder
Ground level safeguarding of circle radius 120 metres centred on aid, and 2% (1:50) slope from ground level at aid out to 450 metres radially.
4.3.10 VHF / UHF Receivers / Transmitters
Ground level safeguarding of circle radius 91 metres centred on the base of the main aerial tower (or equivalent structure). Additionally, from an elevation of 9 metres on this circle a 2% (1:50) slope out to a radius of 610 metres.
4.3.11 Radar and Radio Link Routes
Certain areas of high ground may need to be safeguarded against development in order to protect radar/radio beams. Such areas should be individually specified.
4.3.12 75 MHz Marker Beacons Ground level safeguarding out to 100 metres radially.
4.3.13 NDB
From the centre of the aerial, at a height of 5 metres out to 30 metres radius, with a further slope to a height of 14 metres above ground, out to 90 metres radius.
5 Radio Spectrum Protection Process
5.1 Radio signals may also be degraded by interference from other radio sites, such as a broadcast station whose harmonics conflict with an aerodrome frequency. Protection against the development of a site that could produce such interference is managed as part of the Radio Site Clearance process.
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