Yes, you can just enter your coordinates in NAD83 into Base Mode and use it. I’m not sure what do you mean under scale factor, but I suppose it’s projection parameter. Take a look at this example of projection, there is scale_factor=0.99996.
You don’t need to worry about it when you entering your base position since it’s projection parameter related to the certain State Plane CRS, not to geographic NAD83, and it will be automatically applied by RV3 during transformation.
NAD83 has LLH position that is shared for the whole continent. And this position can be projected to the plane using some parameters, that are responsible for the final plane XY coordinates. The same LLH point in NAD83 can be represented with different plane XY coordinates when you use different projections.
Some tips for converting coordinate systems:
- Use the newest versions of WGS84 - WGS84(WGS 84 (G1762)) and NAD83 - NAD83(2011), they have more precise transformations.
- Use 3D versions (it’s still LLH) of CRSs to prevent from height coordinate stripping. For NAD83(2011) it’s EPSG:6319
- Difference between WGS84 and NAD83 changes in time, so the transformations are time-dependent. For results to be more precise use transformations that include fourth coordinate - epoch when your point was collected
After you set up your base, try to collect some point with known coordinate, eg landmark, to assure that your setup is correct