DG834G-Speed Drops With Antenna

Problem: Netgear DG834G will support 11.Mbps w/antenna or 54Mbps w/out.

834 is set for g-only and is 6 feet away from an Apple iMac (Intel). One is only able to sustain a network speed between 5.5-11Mbps with the supplied antenna attached. 54Mbps is possible when the antenna is removed but (naturally) the signal strength drops 60%. This symptom occurs on any channel.

There are no other 2.4 devices, other than the client computer. There are no other detectable wifi networks on the current channel (4).

Problem exists on both XP and OSX clients.