This is in response to a discussion I had with Jason not too long ago, concerning the function of the rectangular panel that appears on the underside of the new TiBooks.
We had been trying to decide whether it was an AirPort antenna window or a heat sink. I finally had the opportunity to look at the inside of the bottom case, and as it turns out, the panel is in fact a heat sink. The AirPort antennas are still in the same locations as in both previous model TiBooks, which are along the sides of the computer and terminate behind the translucent windows that appear on either side of the case.
The panel on the bottom case, however, is thicker than the rest of the case, and on the inside, covered with a conductive foil to better aid in heat dissipation. This combined with a second fan explains why the DVI models run cooler and quieter than previous models.
Many people seem to be reporting improved AirPort reception with these new models, and the only explanation I can come up with is that Apple has improved the reception quality of the antenna terminals. But I am certain that the panel on the bottom has little to no effect on AirPort signal strength.
