Simple FatMan Mods Scott R. Gravenhorst

Fine Pitch / Fine Pitch Offset

The Fine Pitch Mod consists of simply wiring a 5K pot in series with the original 100K pitch and/or pitch offset control to create a coarse/fine system. The fine control has 5% of the effect that the coarse control has on the associated VCO pitch. When using the new system, always adjust the fine control to mid- range first. Then use the coarse control to get close, trimming out with the fine. This system allows much better control over the flange effect between the two VCO signals. I have an extra panel mounted above and below my FatMan. I positioned the fine controls directly above the coarse (original) ones on the added upper panel. An alternative approach is to replace the 100K 3/4 turn pot with a 100K 10 or 20 turn pot. This is a more expensive method, however.