Transact SQL :: Filtering Out Data

I have a simple query

select distinct
 bl_rec_ref
 ,freq_cd
 from hgmprty1
where(bl_rec_ref is not null and bl_rec_ref not like '%SCH%')

That produces the following output (part shown)

However what I need to show is only bl_rec_ref values where there is no corresponding freq_cd of QTLY.

Looking at the example data above Rows 45 and 46 have the same bl_rec_ref value with a MTHLY and a QTLY value in freq_cd so therefore I don't want this to appear in my output. Similarly with Rows 47 and 48 were the bl_rec_ref has both QTLY and MTHLY values so again should be excluded.

However looking at Rows 51 to 55 which has a bl_rec_ref only showing once for each value of MTHLY and no value for QTLY so these Rows are required in the output.