MCarney said:
The channel # is not part of the legal ID for FCC purposes. A station only has to identify the call letters and city of licence. So if WCVB calls itself channel 5 or channel 20 is of no issue or violation to the FCC.
That's not quite true.
The FCC actually does have rules about channel mapping, though they're not explicitly set out as part of the Code of Federal Regulations. Instead, 47CFR incorporates the standards set by the Advanced TV Systems Committee (ATSC), and one of the ATSC standards (either A/51 or A/65, I forget which now!) lays out the rules for channel mapping.
The short form is this: if your station used to operate in analog, your "major virtual channel number" is your old analog channel number. WCVB has to be 5.x, WHDH has to be 7.x, and so on.
There are standards as well that define what happens if a new station signs on: if the FCC were to license a new station in Boston on the former analog channel 5 frequency vacated by WCVB, it would identify as "20.x."
There is a method to this madness: the goal is to avoid a situation in which multiple stations in a market are all using the same virtual channel number. As we know from WHDH's dual transmissions on RF 7 and RF 42, some receivers can get confused in that sort of situation.
That having been said, the FCC apparently has established an informal policy allowing stations whose former analog channels were above 51 to use their new digital RF channels as their major virtual channels. Since nothing new will ever be licensed to RF 62, there's no harm from allowing WMFP to be "18.x." (If RF 62 were still available for broadcast use, a new station on that frequency would have been virtual 18.x under the ATSC standards.)
They broadcast on digital channel 20 and it maps to channel 5 on a digital receiver box. All stations have put a lot of money into their branding. Why would they throw that viewer identification and goodwill down the drain if legally they don't have to?
This is one of the good arguments for channel mapping in the DTV world.
Mapping is one of those things that causes no end of debate among us geeks. Some of us are just plain bothered by the idea that a station can be operating on "channel 20" and calling itself "channel 5" - but that reflects a now-obsolete way of thinking.
As my friend Doug Smith has observed, there is no such thing as "channel 5" to begin with, at least not in the same sense that there's an "FM 96.9" or "AM 1510." What there
is, is a mapping scheme that was created in the forties and fifties that said "virtual channel 5" is the 76-82 MHz chunk of spectrum.
For the first forty or so years of TV, that sort of fixed mapping was the best technology available, and it was pretty good for the time...no need to know that you had to tune to "614-620 MHz" to find the Bruins game when you could spin the dial to "38" and let the fixed mapping within the TV do it for you.
But for the last decade or so, much of the TV we've watched has been mapped without our even knowing it. If you're watching "channel 5" on your DirecTV or Dish receiver, you're tuned to a digital carrier somewhere in the 12 GHz neighborhood. If you're watching "channel 5" on digital cable, you're seeing a QAM carrier that could be anywhere from 54 to 700 MHz. You don't need to know the technical details behind the transmission, any more than you need to know that the IP address of radio-info.com is 74.201.255.130 in order to find this website, or that the IP address of fybush.com is 66.39.95.174 to find my site.
And here's the fun part: I can move fybush.com to a new server tomorrow if I want, and the underlying IP address will change, but the process will be completely transparent to my readers. What matters is the name, "fybush.com," not the underlying IP address.
It's the same deal now with TV. "Channel 5" is, quite simply, whatever set of frequencies appears on your receiver as "5." The only time the underlying frequency makes a difference is if you're putting up a new antenna or trying to solve an interference problem. In a sense, you could even argue that WCVB doesn't transmit on "channel 20" so much as it transmits on "506-512 MHz, the frequency formerly known as analog channel 20." In Boston, that band of frequencies effectively
is now "channel 5", just as that same band of frequencies effectively is now "channel 52" in Ithaca or "channel 17" in Miami.
As Maureen notes, the channel number is now a matter of "viewer identification and goodwill." When the FCC approved a digital TV system that left some stations on their old RF positions (WMUR, WMTW, eventually WHDH) and moved others to new positions (WBZ, WCVB, WGBH, and so on), the use of mapping became almost inevitable. There's no way the industry would have signed on to a system in which WHDH gets to stay "channel 7," with the 60+ years of brand equity built up in that identity, while WCVB has to ditch "channel 5" to become "channel 20."
And Boston's relatively simple. Imagine Detroit without mapping: the ABC affiliate, WXYZ, has been "channel 7" for 62 years, while what's now the Fox affiliate, WJBK, has been "channel 2" for just as long. After the conversion, WXYZ moves from "channel 7" to "channel 41" - and WJBK, which was digital "channel 58" pre-transition, slides down to..."channel 7." You want to explain that to your TV-watching grandma? I sure wouldn't.
