I have an actiontech router from Verizon. I am unable to use my airport express to extend my wireless network but I can get it to join my wireless network. I entered the password in double quotes as the article suggests but it doesn't solve the problem

Apple designed the AirPort Express to wirelessly extend a signal when it is used with another Apple router.

Therefore, it would be extremely unlikely that the Express would be compatible with an Actiontech....or any other router for that matter if you are trying to extend using wireless only.

The Express can be configured to provide more wireless coverage if a wired Ethernet connection exists between the Actiontec router and the Express.

I got the impression that it was indeed possible if I managed the passwords properly. If I read correctly I need to make the password 13 characters long. Elsewhere I read that I need to enclose the password in ""'s.

Is this still correct? I'm reluctant to change any passwords on the router unless I have a strong feeling it will work.

Unfortortunately, you have "join a wireless network" and "extend a wireless network" confused.

The Express cannot "extend" the Actiontec wireless network to provide more wireless coverage wirelessly.

The Express might be able to "join" the Actiontec wireless network, but it will not provide any additional wireless coverage in this setting. This setting would enable you to connect a printer to the Express or use it for AirTunes....not what you want according to the way that I understand your post.

Apple has recently also made it extremely difficult for the Express to even "join" a network from another manufacturer. Without knowing a lot of details about the inner workings of the Actiontec router, you may not be able to even get the Expess to "join" the Actiontec network.