Collection of 21 ham radio QSL cards mailed to Baltimore operator William Ridenour (W3HI) from 1924-1936.

21 used QSL postcards, approx. 3.25 x 5.5 inches. 12 from the 1920s and 9 from the ‘30s. Generally VG with expected soil and handling wear, two cards chipped at a corner. Includes 20 printed postcards modeled after the standardized QSL format proposed by Donald A. Hoffman in the August 1919 issue of QST ("The official organ of the American Radio Relay League”, p. 29). One plain postcard with a longhand message provides an example of the laborious communication that the standardized format was developed to streamline.

A long-standing tradition in ham radio, QSL cards are (still) exchanged between amateur radio operators to confirm contact and evaluate the qualities of the transmission signals. They record the call sign, location, date & time, frequency, and signal quality. Like exchanging business cards, they served as souvenirs of their contact, occasionally documenting more personal exchanges with jokes in the “Remarks” section, or general expressions of enthusiasm for getting to “QSO” with the recipient. Examples on these cards include, “Sure knocked me for a cocked hat;” "vy sorri to lose you, old man..." and "sure psed to hv clicked... hope to cu on agn.”