My key fob central locking, and opening, does not work outside my house?

I have been having problems with my wireless house alarm, which states that the radio frequency has been jammed, almost every time I go out. A friend has said that his central locking does not work outside my house. Mine has also stopped working more recently and when I use the key manually the alarm goes off when I open the door. I have Sky TV and also have trouble with response from the remote control. Could it be something in my house, or nearby, that is interfering? How can I fix it?