The minimum separation distance of a TV band device (TVBD), operating on channels immediately adjacent to an active digital TV (DTV) channel, from the DTV protected contour is presented. The required keep-out distances for personal/portable and fixed TVBDs are investigated by considering the expected overall propagation attenuation of adjacent channel TVBD signals from the TVBD transmitter to the DTV receiver. The adjacent channel keep-out distances of TVBDs recently announced by the Federal Communications Commission (FCC) are set too long when compared with the case where the keep-out distances are estimated with the free-space path loss model with an additional margin. Adequate adjacent channel keep-out distances are proposed for both personal/portable TVBDs and fixed TVBDs.