Why is my Android phone unable to detect some wireless access points?
If it is an Ad-hoc network

Vanilla Android does not support Ad-hoc Wi-Fi networks. But there is a patch for the wpa_supplicant, that allows you to connect to Ad-hoc networks (root required):


http://www.xda-developers.com/android/android-ad-hoc-wireless-network-support/
http://forum.xda-developers.com/showthread.php?t=754961
http://szym.net/2010/12/adhoc-wifi-in-android/
http://szym.net/2010/12/prospects-of-ad-hoc-wifi-in-android/


But Android 4.0 supports Wi-Fi Direct, which can be seen as a more enhanced version of the Ad-hoc protocol.

If you have an soft-AP

This sounds like you AP is transmitting on a channel that is not avaiable on your Android phones. Try setting the Wi-Fi channel to something &lt; 12 e.g. 5.