The Cone of Confusion is a cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate.
VOR Cone-of-confusion indications:
(1) Size of a VOR cone is negligible, meaning that station passage can be used as a recognizable fix
(2) HSI VOR bearing pointer will be removed when within the cone
(3) HSI VOR CDI will be removed when in the cone
(4) HSI digital VOR bearing numbers will be removed when in the cone
(5) Due to the negligible size of this cone-of-confusion, VOR holding fixes are located directly over VOR stations