phlogiston

Sorry about the links. I understand now.

So, tell me if this makes sense:
The calculated focal point from a parabola assume that the incoming waves arrive perpendicular to opening of the dish. That's middle school math. Well, it dawned on me that this is not the case when you are gathering radiated waves from an (effectively) single point such as an antenna. With my relatively deep reflector I noticed that the signal from near APs was less then that of far ones. That had me stumped until I tried moving the receiver back and forth and found that the focal point was a little different for APs at different distances. After some practice, I was able to mark focal points for different distances and either predict, very roughly, the distance of an unknown, or set it for best reception of a known. This effect will be the same for different shaped reflectors, but seems to be more pronounced when the shape of the parabola situates the focal point even with the opening of the dish. If my math is correct, then having a very shallow antenna (like almost all of those you find on the market) would be best because the focal point wouldn't "move" as much.

Which makes me think that this is already common knowledge. Man, I hate being the last guy in the room to get something.

I wonder if there is any use to being able to measure the distance of an unknown AP without GPS.