Which situation causes reverse sensing on a VOR receiver?

Reverse sensing on a VOR (VHF Omni-directional Range) receiver occurs when the aircraft is flying a heading that is directly opposite to the direction indicated by the VOR's intended course or bearing. This situation arises because the VOR system provides guidance based on the selected Omni Bearing Selector (OBS) setting.

When the aircraft is on a reciprocal heading to the OBS, the VOR indicator will show that the aircraft is moving away from the station instead of towards it. Consequently, if the aircraft is headed 180 degrees opposite the desired bearing set in the OBS, the VOR receiver will indicate a from indication instead of a to indication. This can be misleading for pilots, causing them to erroneously think they are on the correct course when in fact they are not.

In contrast, the other scenarios do not create reverse sensing. Setting the OBS at 90 degrees from the aircraft's location could result in a situation where the aircraft is receiving directional information that does not correspond with its current heading but does not inherently create the confusion of reverse sensing. Failing to change the OBS after passing the station may mislead regarding the desired track, but it does not reverse the indications. Using a non-directional beacon simultaneously does not induce reverse sensing because