QSO

This QSO card from radio-W9JHB, Charles G. Sanner operating from Alpine Street, to radio W6QFB Kyhl Smeby transmitting from Los Angeles, California confirms their QSO on October 10, 1939. The reverse of the card was addressed, stamped, and postmarked on the same day.

QSO. The Q code is a standardized collection of three-letter message encodings, all starting with the letter "Q." These were developed for commercial radiotelegraph communication and were later adopted by other radio services especially amateur radio.

Although Q codes were created when radio used Morse code exclusively, they continued to be used after the introduction of voice transmissions. To avoid confusion, transmitter call signs are restricted.

While an embedded three-letter Q sequence may occur (for instance, VE3QRP is a radio amateur station dedicated to low-power operation), no country is ever issued an ITU prefix starting with "Q." The codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QOZ for maritime use and QRA–QUZ for all services.

QSO card from KDTH