Signal loss

There's a 50% signal loss when I do a speed check at the Express.

Normal and expected if the Express is connecting to the AirPort Extreme over a wireless connection. Remember that the Express has only extend the speed of signal that it receives, and the WiFi signal has already lost a good deal of speed by the time that it reaches the Express.

The Express can help produce a stronger WiFi signal in the area where it is located, but it does not "boost" the speed of the WiFi connection at all as many users seem to think.

A permanent wired Ethernet cable connection from the AirPort Express back to the AriPort Extreme would allow the Express to produce signals in the 100 Mbps range. If your Internet connection plan is faster than that, and you want to preserve the speed on the network, you'll need another AirPort Extreme in place of an AirPort Express.

If you are extending the Extreme with the Express using a wireless connection between them, then a bandwidth loss of, at least 40-50%, is typical. This is due to how the wireless signal is designed to work with Apple base stations.

To remedy this, you would need to use a wired connection between base station, and even with that, the Express is limited to a 100 Mbps Ethernet connection.

You're very welcome!