Note
QST, May 1947, p. 91.
QST, Sep 1947, p. 87. (interesting photo)
Concord catalog 9-47, p. 153.
QST, Mar 1948, p. 110. ("prices slashed")
Officially "Four-20," though advertising often uses 4-20.
Also see Hammarlund 4-11 companion modulator.
Available also as a kit for $39.50. See QST, Oct 1948, p. 109.
References
Technical description. Radio News, May 1947, p. 44.
