AVS Forum Addicted Member
Join Date: Jun 2003
Location: Alexandria, VA, US
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 624 Post(s)
To expand on what foxeng has said, distance separations are dead. Whether a station is permissible is now governed by modeling the stations' coverage and interference and determining whether you're within a rounding tolerance of 0% population. It's not quite that simple, but that's the basic premise.
So yes, adjacency is permitted. To provide a good example, in Los Angeles, there are full powered signals on 31/32/33/34/35/36. They can be all in a row like that because they're all very close together on Mount Wilson or Mount Harvard and at roughly the same power, height, and antenna pattern. At the receiver, then, all the signals look to be roughly the same strength and are easy to pick out. By contrast, also in Los Angeles, KVCR-26 is the only full-power station on a different mountain. As such, the big full-power stations cannot be on adjacent channels. However, there are LPTV/Class A stations on adjacent channels on Mount Wilson and Mount Harvard because they're weak enough that they do not cause interference to KVCR.
So getting closer to home, you'll find that on the NAB Clearinghouse, the FCC's final channel assignment tool has assigned WCCB to channel 18 next to WSOC on 19, and that's because they're at similar location, height, power, and antenna pattern. Similarly, you'll see WCNC on 24 and WJZY on 25 for the same reason. You can't have full powers adjacent to each other at the different locations, but note that WCCB is on 27 and WGTB-CD is on 28 despite being at the different locations. WGTB-CD is weak enough that it does not step on WCCB's signal despite the distance.
Does that help?
Comments are my own and not that of the FCC (my employer) or anyone else.
"Ignorance and prejudice and fear walk hand in hand..." - Rush "Witch Hunt"