I'm not at all familiar with MACs, and it may turn out to have nothing to do with those settings, but...
A wireless Linksys WRT54G with two monster antennas at house #1. A Linksys range expander mounted in the front window sill of house #2. A linksys range expander mounted in the eaves of the roof at house #3. A total distance of about 100 yards. Signal is strong, but connectivity is inconsistent to say the least. The PC's at house #3 are both MACs and I know little about their settings options. The router is using DHCP for ALL attached devices, and I'm thinking that may be part of the problem since the connections at house #3 have to get through two range expanders.
Gurus...What is the best way to program this network and the attached devices to assure consistent connectivity??