Let’s talk about radio navigation, VOR’s, and OBS’s. Three of my favorite things! There are quite a few questions on the IFR written about VORs. And there is one particular question on the IFR written test about checking the sensitivity of a VOR receiver, and how many degrees in course change there should be as the OBS s rotated, all the way, right or left. This is not the same as checking the accuracy of a VOR (you need to check the accuracy this every 30 days if you’re flying IFR). You turn the knob to move the course deviation indicator (CDI) from the center all the way over to the last dot on either side. The selected course should not exceed 10 degrees or 12 degrees on either side. Each dot on the CDI represents 2 degrees.