1997 ford expedition car radio not pick up distant stations

I have a '97 Ford Expedition. Factory radio with CD in console. For years radio worked fine. All of a sudden it will not pick up stations that are farther away on FM. The scan and search buttons will not pick up either. The antenna base does not seem to be corroded. Nothing has changed. Any ideas as to problem?
1. The antenna wire on the back of your unit may have come lose or fallen out. Check that for a start.
2. The antenna may ahve become disconnected from the wire inside the panel of yoru car. Check that too
3. Antenna wire might have become frayed with age, and therefore is not giving 100%. Check the wire all the way back to the antenna.