It is assumed that an aspect sensitivity value of 10 dB/deg is a common and inherent property of any auroral backscatter radar. Based on this assumption the altitudinal profiles of auroral backscatter (APB) are calculated. For radar frequencies smaller than about 70 MHz and moderate to high E layer electron densities the APB's have double maxima structures due to the radio wave ionospheric refraction. For frequencies 70–120 MHz, the APB's exhibit only single-maximum profiles. However, even in this case, there remains an altitudinal control of the APB's by the E region electron densities. It is found that there exists strong restriction on the E region altitudes producing auroral radar backscatter for all frequencies. This effect, which is closely related to the height variation of the zero aspect angle surfaces, also causes variations of the APB with range and azimuth.