Thursday, December 2, 2010

The WSR-74  was a weather surveillance radar which was developed in 1974 for the National Weather Service. It was added to the existing network of the WSR-57 model to improve forecasts and severe weather warnings. There were two types in the WSR-74 series, which are almost identical except for operating frequency. The WSR-74C, which was used for local warnings, operated in the C band, and the WSR-74S, used in the national network, operated in the S band, just like the WSR-57 and the current WSR-88D. S band frequencies were better suited because they were not attenuated significantly in heavy rain while the C Band was strongly attenuated. The WSR-74C used a wavelength of 5.4 cm. It was also fitted with a dish diameter of 8 feet, and a maximum range of 579 km (313 nm) as it was used only for reflectivities.

The WSR-74 was transistor-based and an an updated radar. It introduced to fill a gap in the case one of the vacuum-tube-based WSR-57 radars, which made up a network of 66 radars, went down for maintenance. WSR-74C radars were generally local-use radars that did not operate unless severe weather was expected, while WSR-74S radars were generally used to replace WSR-57 radars in the national weather surveillance network. When a network radar went down, a nearby local radar might have to supply updates like a network radar. Corpus Christi became the first operational site for the WSR-74C on February 1, 1976. More than 70 WSR-74 model radars were spread across the country as the National Weather Service's radar network until the 1990s. They were gradually replaced by the WSR-88D model.