Originally Posted by Scary Des
....coming back through Hurst Narrows one afternoon we couldn’t understand why we could see three yachts about a mile ahead of us through the window and only one large one on the radar. Once they passed the narrows they went there separate ways and became separated blips again on the radar even though one remained far bigger than the others, someone suggested that this was due to AR.
Des, if you already no what I'm going to say then just ignore me. Radar scanner beams have a width and they are slightly diverging. Mine has a beam width of approx 4°. Let's say a target is side on at 2 miles and it represents a viewing angle of 6°. The 4° beam will begin to see it 2° early, it will scan by and it will still see it 2° after. Therefore, the total size of the target painted on the screen will be 2+6+2 degrees, 10°.
In your example of the 3 boats getting closer together as they pass through the narrows, there will come a point where the images on the screen will overlap but the boats will still be 4° apart. Obviously, as the boats separate once through, they will become 3 targets again.
A very narrow target, say, a pole, will have a minimum width on the screen which equals the beam width of the scanner and this is what I would expect the radar enhancer to produce.
There are other variables which will change the width of the image on the screen and most of these can be controlled using the unit's settings. One, which I use extensively, is target enhancement and this artificially enlarges the image on the screen and it is used so one's eye will notice an otherwise small blip on the screen. If it is used where traffic is dense, it will plainly cause overlap of the images and confusion.
The wider the beam, the bigger the image on the screen.
The 63sq metre I think is misleading. My understanding is that the enhancer gives a return strength equivalent to a target of that area not necessarily a target of any particular width.