This sub-series consists of 35 files related to Edward Appleton’s research on Solar Noise. It focusses especially on the period 1945-1947, during Appleton's collaborative work with J.S. Hey, and the favourable opportunity for observations in February 1946. Nevertheless, it also extends considerably beyond these dates to 1936-1951, and includes correspondence and observations from the 1930s noted by radio 'hams' (see especially correspondence with D.W. Heightman (In Coll-37/C.337, and E.J. Williams Coll-37/ C.353) and also continuing correspondence and reports from colleagues. Papers, lectures and notes by Appleton appear in chronological order at Coll-37/C.323-C.328. Correspondence and data from others are presented in alphabetical order at Coll-37/C.329-C.353. Related reports and printed matter appear at Coll-37/C.354-C.357.