Using Airport Express to Extend a Time Capsule Network: Results (*Long*)

Question

Thought I would share my recent (2 hours ago) experience with setting up an Airport Express to Extend a Time Capsule 802.11N 5Ghz Network. Basically I just followed the directions in the Apple Airport Utility, using the "Extend a Wireless Network" setting:
Time Capsule (TC) 802.11N 5Ghz: In computer room
Linksys (LNK) 802.11g configured as dual network router with TC, also in computer room.
Airport Express (AE): In living room, about 50' away, several old plaster walls in between.
According to iStumblr:
1) I get an 80% signal from my TC when my MacBook is practically sitting on top of it.
2) I get an 88% signal from my Linksys 802.11g sitting next to the TC
3) I get 35% signal from my TC when my MacBook is in the living room. This is NOT enough signal, for some reason, to maintain a decent internet connection.
4) I get a 46% signal from my LNK from the same location. This IS enough signal to connect to the network.
5) With the AE configured as "Extend a Wireless Network" to the TC, and placed in the living room (again, about 50' from the TC base station), I get a 55% signal from the AE (which shows up as the same name as the TC network, for obvious reasons) Again, enough signal to connect to the network.
I did some internet speed tests using SpeedTest (take these with a grain of salt, of course)
1) From computer room over TC: 18Mb/s~22Mb/s average over 2 days of testing
2) From computer room over LNK: 18Mb/s~22mb/s average over 2 days of testing
3) From living room over AE(extended network from TC): 5~7Mb/s average in the last 2 hours
4) From living room over LNK: 12~14Mb/s average over 2 days of testing
Preliminary conclusions:
1) Setting up an extended network is pretty straightforward, and works without issue.
2) My 802.11g network with my old Linksys is far superior than my new extended 802.11N 5Ghz network, at least for internet connection speed.
3) I feel a bit irritated buying this AE now to extend my 802.11N network, if its not going to give me any advantages over my ancient 802.11g network
4) File transfers may still be better over the 802.11N-I will test that out at some point.
5) I have not tried WDS instead of "Extend a Wireless Network"-not sure what the benefits would be.
Computer Notes:
MacBook Aluminum-MB(Al) 2.0 C2D (802.11n)
finds 8 wireless networks in my neighborhood (3 of them are mine)
MacBook White-MB(Wh) 1.83 CD (802.11g only)
finds 10 wireless networks in my neighborhood (3 of them are mine)
Oddly, the signal strength of my networks isn't that different between the two computers-between 2% and 5%, even though it can't see as many networks. The 2 networks the MB(Wh) CAN see are at around 21% and 25% signal-not sure why the MB(Al) can't see them at all.

Answer 1

Your biggest mistake is confusing signal strength with signal quality. The signal indicator indicates strength and nothing else. You need to be using iStumblr to look at SNR (Signal to noise ratio).