And Triax even allows wasting part of the dish for nothing, as the effective area of the dish sits above the arm extending from the face.
I've thought about that in the past, too.
I would think that ~apart from the fact that the signal cannot get
through the arm itself, so the little square of dish surface beneath it is in fact useless indeed~ the rest of the lower 'rim' of the dish would just as much reflect the satellite signal to the focal point of the dish, as any other part of the dish. So I would think that that part can also be used as effective dish area.
@Trust1 showed some time ago that the LNB aiming point of the standard LNB holder of a triax 64 would be at the G-spot
of only the effective area ABOVE the arm (see
).
But that design choice doesn't mean the rim below that area (apart from under the arm itself) cannot be used as effective area.
I'm not sure what the f/D of the dish is supposed to be (with and without the lower rim), though. But with an LNB with matching f/D-ratio, and with aiming the LNB a little bit lower, the total dish surface can be used as effective area I would think.
Maybe that area IS already used in practice, even; as from what I've read the exact aiming point of an LNB isn't that quintessential.
I've never read about tests where people had wet cloths on the lower rim, to test the difference, alas. :-(
Greetz,
A33
Edit: Ah! The youtube link shows as a movie, not as a link! The wonders of internet technology....