The SDS100 receives signals with good strength several 100KHz off frequency and you might have some pager signals that interfere. The exact offset depend of the filter settings, Normal, Invert and so on and also IFX, so try that first.
If you receive your 150MHz channel with a signal strength of -80dBm or stronger you can enable the attenuator on that frequency to also reduce the signal strength of the interfering signal .