finding best location for T-Mobile home Internet gateway

Well, last night I was trying to improve my reception, when I noticed that the tower CGI had changed since the T-Mobile rep had reset everything, and the current tower location was on the opposite side of my house from the original one, so I disconnected the gateway and moved it to a window on the other side of the house. That helped, had 3 bars showing instead of 2, but the internet speed only slightly improved, was still only about 5 Mbps. This morning when I got up and checked it on a few different servers, I got as high as 117 Mbps, but also as low as 24 Mbps. The problem with where the gateway is now is that it is so far away from my TV that the ethernet cable doesn't come close to reaching, and the wifi refuses to stay connected to it. Nothing's ever easy.