S band
There are two types in the WSR-74 series, which are almost identical except for operating frequency. The WSR-74C (used for local warnings) operates in the C band, and the WSR-74S (used in the national network) operates in the S band (like the WSR-57 and the current WSR-88D). S band frequencies are better suited because they are not attenuated significantly in heavy rain while the C Band is strongly attenuated, and has a generally shorter maximum effective range.