How to Calibrate the PL660 on the FM Band ?

There is a Hidden function of the PL-660 : You can calibrate the FM Frequency the following steps:
There is a hidden function of this radio: You can calibrate the FM frequency by yourself, is that cool ? Yes, here it is how to do it :
Re-calibrating FM, radio needs to be on and set to FM band. Tune to the desired frequency/station you wish to listen to, press "SYNC" for about 3 seconds back light will flash. Tune up until the frequency/station sounds more clear press "1" to confirm re-calibration. If done correctly the correct frequency/station will be displayed on the display. Keep the battery in for all the time..