This installment of Found in the Attic examines the Hallicrafters S-20 'Sky Champion' receiver. The 'Sky Champion' line was the company's' mid-priced communications receiver. Introduced in 1938, the S-20 was replaced by the S-20R in 1939. Since it was in production for less than a year, these receivers are somewhat rare.
There are several differences between the S-20 and S-20R. The S-20 primarily used tubes with grid caps, while the later S-20R used newer replacements. Tube lineup for the S-20 includes: 6K7, RF stage; 6L7, 1st detector-mixer; 6J5, HF osc; 6K7, IF amp; 6Q7, 2nd detector-AVC-1st audio stage; 6F6, audio out; 6J5, BFO and 80, rectifier.Read More