Garmin GNS 400W Pilot's Manual & Reference page 211

APPENDIX C
Troubleshooting Q & A
Why does my CDI not respond like a VOR when OBS
mode is active?
Unlike a VOR, the CDI scale used on GPS equipment
is based on the cross-track distance to the desired course,
in OBS mode not an angular relationship to the desti-
nation. Therefore, the CDI deflection on the GPS will be
constant regardless of the distance to the destination, and
will not become less sensitive when you are further away
Full-Scale deflection and defined path for normal approach
from the destination.
Sensitivity must change from ±1 NM FSD to either ±0.3 NM or
±2° FSD, whichever is less at the FAF. Change occurs over 2 NM
and is completed at the FAF.
1 1
NM NM
Full-Scale deflection and defined path for VTF approach
2 NM 2 NM 2 NM 2 NM
CDI Comparison: GPS vs. VOR
190-00356-00 Rev G 201