As Westhawk pointed out, the radar antenna's beam width is not linked to brand but antenna size.
A 30" diameter flat-plate antenna will produce about 3 degrees of beam width. a smaller diameter would give a wider beam. Now that is for flat-plate. For other shapes, results may differ, but in commercial aircraft I believe this to be almost exclusively flat-plate antennas.
Although I don't know the whole product range of Collins, I suspect they offer radar equipment to fit in various aircraft size, and give options for different flat-plate diameters.
A reference section regarding angle, distance and beam width of radar equipment can be found in the book "M3: Mental Math for Aviators". Of course other sources can be found online too.
newifr, which aircraft is your Collins equipment mounted on? Do you know the antenna diameter?
Last edited by Jetdriver; 3rd Nov 2013 at 14:52.