Quadrantal error does not affect signals from straight ahead or behind, nor on the wingtips.
It is sometimes wrongly confused with quadrantal error, which is the result of radio waves being bounced and reradiated by the airframe.
The further from these cardinal points and the closer to the quadrantal points ( i . e . 45? 135? 225?and 315?from the nose ) the greater the effect, but quadrantal error is normally much less than dip error, which is always present when the aircraft is banked.