Network is created with extreme, devices dont see expresses

Question

Hello everyone, i will try to explain my dilemma as clearly as possible.
Recently we recived the 2WIRE u-verse ATT router, which is terrible on giving a wireless signal.
So i decided to buy an airport extreme, and 2 expresses.
I disabled the wireless of the 2Wire router,
Then set up the network with the Extreme,
and placed the expresses in the room that has terrible signal.
(other rooms do not have any ethernet ports, but do have the phone line things on the walls)
The issue that i am having is those two other rooms.
The room with the Aiport Extreme is fantastic, and runs smoothly.
And yet my iPhone and iPads, cant receive a signal, the computer can but its so slow. And yet the Expresses are in those rooms.
The Expresses are set to extend the range, and the signal to the extreme is "excellent"
The ony information i could find to resolve this is to buy a powerline adapter, is that the only way?
If so/If not, how do they work?
I did every confiquration possible, very rarely the connection would be great, but dead again the next day.

Answer 1

Without knowing the exact layout of your home, it may be possible that both of the 802.11n AirPort Express Base Stations (AXn) may be just outside of the useful signal range coming from the 802.11n AirPort Extreme Base Station (AEBSn) to successfully extend it.
One way to find out, is to make Signal-to-Noise (SNR) measurements at the locations where the AXns are placed to see if the signal quality is sufficient enough.
SNR (in dB) = Signal (in dBm) - Noise (in dBm)
For example, a signal level of -53dBm measured near an access point and typical noise level of -90dBm yields a SNR of 37dB, a healthy value for wireless LANs.
SNR Guideline
40dB+ SNR = Excellent signal
25dB to 40dB SNR = Very good signal
15dB to 25dB SNR = Low signal
10dB to 15dB SNR = Very low signal
5dB to 10dB SNR = No signal
If you have a Mac laptop handy, I suggest downloading a copy of iStumbler. You will use iStumbler's Inspector feature (select Edit > Inspector from iStumbler's menu) to capture the Signal & Noise values.  Be sure to power-off each AXn as you only want to measure the SNR of the AEBSn. Start with your laptop near the AEBSn, note the readings, and then, take the same measurements at each of the locations where the AXns are placed.
The SNR, as measured from the laptop, decreases as the range to the base station increases because of applicable free space loss. Also an increase in RF interference from microwave ovens and cordless phones, which increases the noise level, also decreases SNR.
If the SNR is 25dB+ at each of these locations, then you should be getting reasonable signal quality from the AEBSn at all of these locationst. If less, either try to locate the source of the Wi-Fi interference or try relocating either of the AXns until they are within a 25dB SNR range.
If, after relocating the AXns, you still do not get a high enough SNR, then you may want to consider employing Powerline adapters.