Q: Unstable Wi-Fi with Time Capsule + Express Booster

What is the make & model of the Internet modem that Comcast is providing you that your Time Capsule (TC) is connected to via Ethernet? Where is the AirPort Express located in relation to the TC? Same room, different room, or different floor? Are they interconnected by wire or by wireless?

Try unplugging the MODEM for a while, but don't worry about the extension, only move it a little closer, Just your MODEM, wait about 10-30 seconds, plug back in. Open Aiport utility a little while later and wait for the network and airport labels to have green dots next to them.

i Had the same exact problem yesterday and this solved my problem. (I have the same setup, too.)

Ok, thanks for the additional information. The TC8350C is a combination modem & wireless router or gateway device. In this case do you have the TC reconfigured as a bridge? Also, is either the TC or the TC8350C or both broadcasting a wireless network? If both, are they configured as a roaming type network? Finally, is the Express configured to extend or join this network?

With the TC and the gateway connected by Ethernet, the TC needs to be configured for a roaming network. This type of network allows you to "extend" the wireless range using Apple & non-Apple products. In this type of network, the "main" router (your TC8350C) must be configured as a router and all other devices connected to it must be configured as bridges. This is basically what you have now.

I believe the issue is how both the TC and Express wireless are set up. The TC should NOT be configured to "extend a wireless network." Instead it should be configured to "create a wireless network." Only the Express should be configured to "extend."

Let's start by powering down both the TC & the Express. Verify that you do not have any wireless connectivity issues with just the TC8350C. If you still do, then we need to take another troubleshooting path. If not, then we will "start over" by first configuring the TC properly with the gateway for a roaming network.

I unplugged both the TC and Express.  I can't find any wireless to connect (except for xfinity, but I'm pretty sure that's the unsecured hotspot).

Yes, the wireless network you should now see is being provided by your gateway device. Whether or not, it is unsecured will depend on how it was initially set up by the Comcast technician. They should have provided you with an opportunity to set the wireless security password at that time. However, it is still something that you could do if they did not.

I was to be sure that you can access the Internet connected by either wire or wireless to this gateway before we proceed. You will also want to know the network name (aka SSID) and wireless security type (WEP, WPA, or WPA2) & password for the wireless network that this device is providing before we can proceed to adding back your other devices.

The best way to determine the security type is to access the gateway via its web-based administration page. You should be able to gather any current configuration details. That's, of course, Comcast allows you to administer the gateway they provided you. Otherwise, most likely, it is configured for either WPA or WPA2 security.

The key here is to connect to this network to verify that you can gain Internet access via a wireless connection. Can you?

Ok, great! You have, at least, established that you can get an Internet connection with the Comcast-provided device for both wired and wireless connections.

You will also need the following information from the TC8350C for the next series of steps:

• Wireless Network Name
• Wireless Security Type
• Wireless Security password

Let's get to the next step and that is to configure the TC8350C and the TC into a roaming type network. Start by keeping both the TC & Express powered-off. (Note: We will get to the Express as the last "step" and concentrate on just the other two devices.)

• Perform a "factory default" reset on the TC. After it has completed, power it down.
• Now connect an Ethernet cable between one of the Ethernet ports on the TC8350C to the WAN (circle of dots) port on the TC.
• Power-up the TC. Give it about 5 mins to initialize.
• Run the AirPort Utility on your Mac or iPhone.
• Select the TC, and then, select Edit.
• Go to the Network tab. Change Router Mode to: Off (Bridge Mode)
• Go to the Wireless tab. Verify or change the value for Network Mode to: Create a wireless network.
• Enter the wireless network name you noted above in the Wireless Network Name field.
• In the Wireless Security field, select "WPA/WPA2 Personal."
• In both the Wireless Password & Verify Password fields, enter the wireless security password from above.
• Click on Update, and allow the TC to restart.

Once restarted the TC will broadcast its own Wi-Fi network, but since it will use the same network name, security type, & password of your TC8350C"s network, any wireless network client will just "see" a single Wi-Fi network with that network name. Does it?

If so, then again verify that you can gain Internet access with this set up. (Note: Do not set up the Express yet.) Please post back your results.