Do you have the AirPort Express located at a point that is about 1/2 the distance from the AirPort Extreme and the general area that needs more wireless coverage?
The Express can only "extend" or "repeat" what it receives and make that bandwidth go further. It does not "boost" the signal. So, if it's located too far from the AirPort Extreme, it is not receiving enough signal to extend effectively.
Anything you can do to minimize obstructions....walls, ceilings, etc in the signal path will also help the strength and bandwidth of your wireless signal. Even a typical wall in a home of sheet rock and 2 x 4s will on average absorb 15-20% of the signal, so if you have more than a few walls in the signal path, you are losing a great deal of signal.
If there are too many obstructions in the signal path, you may need to look at another Ethernet method to "extend" the wireless signal to provide better coverage to the remote areas.
Yes, the airport express is about half way, and yes, it gets a decent signal from the main airport extreme (Signal -59, noise -84, rate 115) Like I said, it works fine, for a bit, then all of the sudden NOTHING could associate with it.
Even if the airport express was too far from the main base station, devices should STILL be able to associate with it, just maybe not pass any traffic. If I'm connected using the airport utility, and watch, NOTHING is connected to it.
A Signal of -59 dBm minus noise of -84 dBm would yield an SNR of 25 dBm, which is right on the edge as far as a decent signal would be concerned. 30-35 would be desirable, if possible.
If things seem to work fine...then all of sudden go south, there are several possibilities for this:
1) The Express is picking up some form of intermittent wireless interference from another cordless phone, wireless network, or wireless camera/security system. Any of thes devices could be at the neighbors, for example like a situation that I've experienced in the past when I discovered that my neighbor...across the street....could knock out my "extending" Express if he was in his front yard talking on his cordless phone.
2) The Express is overheating internally and this is causing a problem with an electronic component that causes a loss of connection with main base station.
Even if the airport express was too far from the main base station, devices should STILL be able to associate with it, just maybe not pass any traffic.
I don't think this is correct. In 3 tests here when I purposely located an Express well beyond the point where it could not pick up a signal from the main base station, devices would not associate with the Express. How could they if the Express was not "extending" a signal that the devices could pick up?
As far as the numbers I gave, I would NOT say it "is right on the edge as far as a decent signal would be concerned". In fact, I would say those numbers are fairly decent for a wifi network.
Here is corroboration:
- > 40dB SNR = Excellent signal (5 bars); always associated; lightning fast.
- 25dB to 40dB SNR = Very good signal (3 - 4 bars); always associated; very fast.
- 15dB to 25dB SNR = Low signal (2 bars); always associated; usually fast.
- 10dB - 15dB SNR = Very low signal (1 bar); mostly associated; mostly slow.
- 5dB to 10dB SNR = No signal; not associated; no go.
These values seem consistent with testing we've done in the past, as well as what some of the vendors publish."
As well as the fact that as soon as I reboot the airport express, everything starts working as it should.
I have not tested my hypothesis with devices still being able to associate with an airport express that is too far away from the base station. But I believe it is doing WDS with the main base station. If that is the case, devices should STILL be able to associate with it, even when it is too far away. That is NOT to say they will have internet access, but will at least be able to associate with the airport express. I will try to test this later today...