Randy, I found the ATU memory step spacing in the Firmware Release Notes. In release notes for MCU 3.03 / DSP 2.10, 3-17-2009: * MULTIPLE KAT3 ATU DATA SEGMENTS PER BAND/PER-ANT.: 10 kHz per segment on 160 m; 20 kHz on 80-12 m; 50 kHz on 10 m; 200 kHz on 6 m. John, KN5L