See the steps below to correct the signal strength values
1) Press PGM ( PROG)/ Func/F3
2) Use the Down Arrow to scroll to RSSI Sig Cal Press SEL
3) At Bar 1 change # to 190
4) Press Down arrow to Bar 2, Change # to 230
5) Press Down arrow to Bar 3, Change # to 260
6) Press Down arrow to Bar 4, Change # to 290
7) Press Down arrow to Bar 5, Change # to 320
8) Press F1 to Save
9) Press F2 to Exit
10) Press SCAN button to start scanning again