How to extend your wireless Apple network????

Yes, an Airport Express can be used to extend an AEBS network. But if you put it in the same location as the computer then it will receive just as weak a signal as the computer does. You need to locate it perhaps mid-way between the AEBS and your attic, but not farther than 150 feet of unobstructed space from the AEBS. Walls, ceilings, floors, etc. all attenuate a WiFi signal.

Yes. It's easy.

Read this KB article: Wi-Fi base stations: Setting up and configuring an extended wireless network (802.11n)

Here is the relevant excerpt:

Set up: Components of an extended network

➊ Primary Wi-Fi base station (this is the base station connected directly to the Internet)
➋ Extended base station

Configuring a wireless extended network

To create a wireless extended network, you must place any extended Wi-Fi base stations within range of the primary Wi-Fi base station.

Start with the device that will be configured as the primary Wi-Fi base station. Then configure your extended Wi-Fi base stations, ensuring that each is within direct range of the primary Wi-Fi base station.The physical location of extended Wi-Fi base stations will vary according to the building environment and may require some experimentation.

If you have configured your Wi-Fi base stations in the past, it may be helpful to do a factory default reset of each Wi-Fi base station that will be part of the wireless extended network before you begin.

Configuring the primary Wi-Fi base station

1. Power on all 802.11n Wi-Fi base stations and allow them time to appear in the AirPort Menu Extra.
2. Open AirPort Utility (On a Mac, choose Go > Applications from your desktop, click the Utilities folder, then open AirPort Utility. In Microsoft Windows, choose Start > All Programs > AirPort to start AirPort Utility).
3. Select the primary Wi-Fi base station in the Base Station Chooser, then click Continue. Note: If you see a message appear that indicates that the Wi-Fi base station has been reset, click Cancel to continue.
4. Click Manual Setup. Enter the base station password if necessary.
5. Click AirPort in the toolbar.
6. Click Wireless.
7. Choose “Create a wireless network” from the Wireless Mode menu.
8. Select the “Allow this network to be extended” checkbox.
9. Enter a Wireless Network Name.
10. Optional: By default, Wireless Security is set to None so that no password will be required to join the network. We recommend you click on the Wireless Security menu, select WPA2 Personal, and create a password between 8 and 63 characters long.
11. From the Radio Channel Selection menu, select Automatic.
12. Click Update.
13. The next window may indicate that there are some problems. Resolve the problems, then click Update.

You are now ready to add extended Wi-Fi base stations to your network.

Configuring an extended Wi-Fi base station

1. Place any extended Wi-Fi base stations within range of the primary Wi-Fi base station
2. Ensure that all 802.11n Wi-Fi base stations are powered on and allow them time to appear in the AirPort Menu Extra
3. Open AirPort Utility (On a Mac, choose Go > Applications from your desktop, click the Utilities folder, then open AirPort Utility. In Microsoft Windows, choose Start > All Programs > AirPort to start AirPort Utility).
4. Select the Extended Wi-Fi base station in the Base Station Chooser, then click Continue. Note: If you see a message appear that indicates that the Wi-Fi base station has been reset, click Cancel to continue.
5. Click Manual Setup. Enter the base station password if necessary.
6. Click AirPort in the toolbar.
7. Click Wireless.
8. Choose “Extend a wireless network” from the Wireless Mode menu.
9. Choose the network you want to extend from the Network Name menu.
10. Enter the network and device password if necessary, then click Update.
11. The next window may indicate that there are some problems. Resolve the problems, then click Update.

There's no real point to buying a second AEBS when an AEX will do. But you need to install the AEX in a strategic position so it gets a good signal from the AEBS to resend to the attic.

Configure the AEBS wireless to allow its network to be extended - it's a checkbox. Configure the AEX to extend an existing network. Both are done using Airport Utility.

You'll save $30 if you buy a refurb.

However, others have told you NOT to place the Express in the attic. The Extender Express is a repeater. It receives a signal from the main unit, decodes it and then retransmits it. If it's located in the attic, it won't receive a decent signal from the main unit. You should put the Extender in a location where it can receive something worth retransmitting. My WAG is that you will get the most benefit if it's located half to 2/3 of the distance to the attic.

The setup takes all of five minutes with Airport Utility.

Look at it this way. The extender can only extend what it receives. If it receives garbage, it will extend garbage. Is that what you want?

Further, where are you trying to extend the WiFi signal to? IF you receive a good signal in the attic, then you can put the extender there and extend the signal to thirty or more feet above the roof! Who is going to be up there to use the signal?

I understood your first post to mean that you want to receive a good signal in the attic. That means that the extender must be SOMEWHERE ELSE (closer to the main unit where it can receive something worth extending).

As we've tried to stress and as the diagram you see in John Galt's post you need to have the AEX located near enough to the AEBS to get a strong signal yet also closer to your attic. As the diagram shows they should be placed where the signals are overlapping.

Each device has a maximum free space range of 150 feet. However, walls, floors, ceilings, etc. attenuate the signal such that they may have an effective range of, say, only 50 feet. That means the two devices have to be close enough for a strong extended signal. You may need to situate the AEX not more than 20 feet from the AEBS and not more than 20 feet from the attic to assure that. It may take some testing to find the best location for the AEX.