SX-101 and SX-101 MK1: have 11 and 160 meters; no product detector

SX-101 MK2: same as above plus improved stability

SX-101 MK3: same as above plus oscillator filament is always on

SX-101 MK3A: same as above except 160 meters dropped, 6 & 2 M converter position added, 11 meters retained

SX-101A: 160 and 11 meters dropped, converter position added, product detector added, full 10 meter bandspread

The 101A had IF frequencies of 1650 & 50.75, while the SX101's had IF frequencies of 1650 & 50.5.