I have this frequency listed for Delaware County Fire as Secondary Districts 9 and 10. I've never heard it used before. It used to be Fire 10 but I think Fire 10 is now 506.6625 (Upper Darby Channel). This channel makes a "errerrerr" kind of noise when my scanner picks up the squelch. I looked this frequency up and found that the nearest user other than Delaware County who uses this frequency is Ocean County, NJ. I souldn't be picking up anything from that far away in Delco. Any idea as to whether or not I should keep this channel programmed?