Note
QST, Jan 1976, p. 106.
QST, Apr 1977, p. 157.
QST, Apr 1979, p. 113. (more info)
QST, Apr 1980, p. 176.
The Ten-Tec model 509 arrived in 1976. It retained the basic flavor of the original Argonaut, with its QSK CW, no-tune broad-band amp, built-in SWR/S-meter, RIT, and direct frequency readout.