Most 2.4GHz systems work better if their base stations are up high in relation to the user-like on top of a bookshelf. The antennas are omnidirectional, but since the antenna on your computer could be in the base or screen, or sticking out the side of a laptop, or stuck inside an iMac in an adapter, it usually helps to put the antenna at a slight diagonal to vertical (both front to back and sideways). This increases the chance that the signals will be effectively sent and received by the clients.