MacBook – Loosing WiFi router connection when moving from one router to another

Try using iStumbler to detect and identify neighboring and overlapping wireless access points (WAPs). It's likely an interference issue that can be solved with vigilance. You need to find out what channels your neighbor's WAPs are using, and then switch your router to use the least crowded channel you can find.

Ideally you want to use channels 1, 6, or 11. These are the channels that have the most leeway when it comes to other channels interfering with their signal. Wifi devices operating on a particular channel can interfere with other devices operating on channels up to 5 steps away. The amount of interference grows logarithmically with signal strength and channel proximity.

For example, if you are using channel 1 and your nearest neighboring wireless network is also using channel 1, you are receiving a large amount of interference. If you are on 1 and the other network is on 6, the interference is negligible. However, if you are on channel 1 and your neighbor is using channel 3, you are likely still on the receiving end of a huge amount of interference depending on their WAPs signal strength.

iStumbler will give you information about the signal strengths emanating from the other interfering WAPs, and from there you can infer the best channel to use. You may need to periodically perform the same task as your neighbors change their wifi channels.

Don't have the solution but have interesting observation!!

My WiFi scan shows the SSID that I want to connect to

and in Terminal the Airport -s shows same SSID

I was monitoring the Console during the event.

The Associate event still shows the Correct SSID

<airportd[535]> associate: INFO: airportd associate: network=<CWNetwork: 0x7fec12802ce0> [ssid=Eurona900850808-81, bssid=02:0c:42:39:95:94, security=Open, rssi=-80, channel=<CWChannel: 0x7fec12802cf0> [channelNumber=7(2GHz), channelWidth={20MHz}], ibss=0], is8021X=0, remember=1

After few lines of other WiFi activity this comes up:

<kernel> Searching for networks with ssid Eurona900850808-8

WAIT: where did the last digit go, it supposed to be the Eurona900850808-81, but it shows Eurona900850808-8

Here is the rest from the Console:

Fri Sep 13 23:22:55.92  <kernel> Searching for networks with ssid Eurona900850808-8
Fri Sep 13 23:22:57.488 <kernel> No networks found. Please check if the network exists and is in range
Fri Sep 13 23:22:57.488 <airportd[535]> _WiFiMT_LogAssocTimeoutFail: MT** Assoc Timeout
Fri Sep 13 23:22:57.488 <airportd[535]> associate: Apple80211Associate2() failed with error -3905

Clearly the SSID lost the last digit somewhere in the process, and that leads to the Famous Timeout Error at least in my case.

While Apple provides great tools to analyze the WiFi, it is lacking bit more descriptive Error messages, like in my case saying there is no such network available since it clearly knows that in the Console report.