The swept-frequency receiver is one of the most powerful tools for studying the processes that go on in the sun's atmosphere. However, the instrumentation becomes fairly elaborate if a large frequency range is to be covered by such an apparatus. Consequently, only a few such receivers have been built, and those that are in operation are somewhat limited in their frequency coverage. It then seems worth while to examine the data from existing fixed-frequency receiving stations in order to determine the extent to which they can supplement or approximate the results of the swept-frequency apparatus. Many solar observations at fixed frequencies have been made and are still being made by numerous observers. These data contain much meaningful information if they can be interpreted successfully.