Searched online to find some schematics of step attenuators and then edited schematic into QUCS.
Simulator result
DB
| Volts | Expected DB | Calc DB |
| 5 | ||
| 4.46 | 1 | -0.99 |
| 3.55 | 3 | -2.97 |
| 2.52 | 6 | -5.95 |
| 1.26 | 12 | -11.97 |
| 0.403 | 22 | -21.87 |
| 0.0675 | 42 | -37.39 |
The +20 db step is off quite a bit.
