distantpulse: The radio will lock on to the strongest signal it can find on a given frequency. In your case it probably is getting interference on 89.7 and is picking the next pest station for you to listen to. Switch the radio to manual tuning (hit the "man" button) or alternatively use a different frequency. Here's a handy little link that will help you find unused FM frequencies in your area:

Courtesy of MIT:

http://radio-locator.com/cgi-bin/vacant