When I added an external antenna to my AirPort base station, the antenna instructions noted that the WiFi "space" that it projects is shaped like a big oval instead of a round sphere. Therefore, it extends the signal better across my second floor than down to the first or up to the third. Does the AirPort Express create a spherical space or an oval space? If an oval, should it be plugged into the wall (like Apple shows in the pictures) or can I plug it into a surge protector on the floor? Strange question, but I have a 110 year old masonry home and needed to add the antenna to the Graphite station to get full coverage in the house.