  We observed the ZZ Ceti star GD 154 over a whole season at the mountain
station of Konkoly Observatory. Our long time base allowed to detect the sign
of rotational triplets around the independent modes. To check whether these can
be real detections we made a test on our data set. We searched for
characteristic spacing values performing Fourier analysis of numerous peaks
determined around five frequencies in the main pulsation region. The analysis
revealed regular peak spacings with separations around 3.7 and 2.6 microHz.
These values are in accordance with the ones determined by consecutive
prewhitening of Whole Earth Telescope observations.
