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Diagram 18 RCS calculation at LoS +20m (-158dB Path loss)


74. At 20m higher than the LoS height, the required RCS to produce a detectable signal is around 37.5m2, which is entering the range where the radar might reasonably be expected to begin to detect the turbines and is a reasonable RCS to assume for the blade tip for this size of turbine. This does assume the maximum on-axis antenna gain of the radar. Cromer Radar uses a modified Cosec2 antenna system which has reduced gain at lower angles to reduce ground and sea clutter. A reduction of just 5dB antenna gain at the turbine elevation angle (-0.25° from the radar) would make the detectability at LoS +20m extremely unlikely.


75.


Based on these findings, Cromer PSR would not be expected to detect turbines up to 20m above the LoS heights. As the Cromer radar LoS at the closest point of the East Anglia THREE site, being the North West corner, is 204m AMSL, this modelling supports the conclusion that the East Anglia THREE site could accommodate 220m turbines across the entire area and would require no further mitigation.


16.7 Conclusions (including potential mitigation) 76.


The following paragraphs draw together the conclusions of the radar modelling undertaken in this Appendix and set out the areas in which mitigation may be required if turbines of specified heights are utilised.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Appendix 0 Example Page 20


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