Where I live I can, for the most part , receive 3 DMA's , Roanoke ,VA, Raleigh, NC, and Greensboro, NC. Many times , I cannot get Roanoke FOX because Raleigh NBC also broadcasts on 17. There is a county in VA, Halifax , that is in the Roanoke DMA and the neighboring country in NC, Person, is in the Raleigh DMA.
If Media-General had wanted to spend the money, they could have put WNCN on channel 45, but they probably didn't want to put up a new antenna for that channel given a perfectly good channel 17 antenna was already up there. Fortunately, most viewers can see WSLS for NBC and WWCW or WRAZ for Fox. It also works out that, because of the terrain, WFXR tends to be pretty solid in most of its coverage area, while WNCN tends to get stomped on by WFXR in the northern parts of its coverage area. My parents have only rarely had WFXR taken out by WNCN. Much more common is WPXR wiped out by WUNP.
Charlotte NC and Raleigh NC have channels that share a frequency also.
Only two real cases. WCCB/WRDC on 27 were assigned that way by the FCC, assuming the two would be using less power than they are now using. (WCCB at 86.5 kW instead of 1000 kW, WRDC at 226.3 kW instead of 725 kW.) WTVI/WTVD on 11 came about because WTVI was assigned to 24 and would have received a lot of interference from WBTV on 23. There really wasn't a better option available for WTVI, and being a struggling non-commercial broadcaster that needed to save money and not have to rebuild after the transition.
I am sure that many of you understand that when there is co-channeling , there is no channel at many times.
Is this common? I remember the FCC used to be very strict on full power TV stations and interfering with each other. Maybe they have stopped caring so much because most people watch cable or satellite .
It's somewhat common. The worst one, in my opinion, is WFSB and WCBS both on channel 33. Good luck watching CBS from either one half-way between the two of them.
The rules used to be distance-based, but if that had been kept during the transition, stations never would have been able to go digital. There wouldn't be enough channels to assign every station a second channel to go digital while keeping the distance rules, even taking into account that digital doesn't have interference issues except for the co- and adjacent-channel cases, whereas analog could have interference as far as plus or minus 15 channels. I don't necessarily agree with the method that was chosen (and I work for the FCC), but hard distance rules weren't the right answer.
In my opinion, some of the worst cases are:
WFSB/WCBS on 33
WNYW/WMCN/WDPB on 44
WCVB/WCCT on 20
WFXT/WTIC/WPXN/WPPX/WSWB on 31
WMPT/WTXF on 42
WITF/WTTG on 36
WFME/WUVP/WMPB on 29
WUNP/WFPX/WPXR on 36 (I've been to a place where you can turn the antenna one way, see WPXR, then turn it the other way and see WUNP.)
WJZY/WZRB/WCSC on 47
WPGX/WALA on 9
WOIO/CFPL on 10
WFFT/WLNS on 36
WFWA/WKAR on 40
WGN/WMTV/WHOI/WXMI on 19
WSNS/WLLA on 45
KSNW/KOTV on 45
KFWD/KCEN on 9
KHOU/KVCT on 11
KSCI/KUSI on 18
There are probably many more that could be problematic, of course.
- Trip