Originally Posted by
Spiney Norman
Jeez! That must have been fun! My experience of the 264 never included 2nm SRAs but the primary blip size must have been around a nautical mile wide!
In the '70s, Glasgow only had a 264 so all SRAs were done on that (2nm only)
As regards termination range, it depends on what 'setting up' markers are installed and whether they are simple 'reflectors' or they generate an electronic signal which 'breaks through' MTI.
For a half mile SRA, you need a marker either side of the runway at the touchdown point (plus a minimum refresh rate of 15(?) rpm). The markers must show permanently whether or not your radar has MTI.
For a 1nm SRA, you must have one or more markers on the runway centreline but they do not need to be permanent so you can check the setup on 'raw' radar then select MTI.
For a 2nm SRA, no markers are required.
In this latter case, when using Pease Pottage radar on Farnborough LARS East, I often watched aircraft in the circuit at Shoreham down to just above ground level according to their altitude readouts; the radar being about 350ft amsl just south of Gatwick looks through a gap in the South Downs and it would be perfectly feasible to do a 2nm SRA to runway 21 (threshold elev 7ft amsl) using it even though it is a long way from the airfield.