This modem can't be disassembled because it's all-in-one machine.

According to your configuration, it seems the extender hasn't been configured successfully. Have you tried with another laptop? When you use wired connection, do all the devices work only you disable...

Generally speaking, we need to replace both antennas if we want to change antenna. If we just change one of them, there is no much difference. It seems there is no way to choose a frequency.

Do you have any issue with current driver on win7?

in that case, we can directly hard reset the device into factory default and reconfigure it.

Make sure your pc/laptop is connecting to the extender's wifi not your main router. If you connect your pc/laptop to the extender via a cable, please make sure it doesn't connect to the main router's...