davisdynasty83 asked [TD V24#116]:
An excellent narrative on this subject is "Whatever Happened To Channel 1" by David A. Ferre (Radio-Electronics, March 1982,43-46,89). PAT added the following comment:
Indeed. Except for channels 2-13, cable TV channel-number assignments differ in frequency from same-number broadcast channel assignments. A CATV Frequency Assignment chart is posted atMy previous post about Cable Channel 1 is at Michael Quinn wrote [TD V24 #117]:
Historical accident, cultural inertia, administrative convenience, and commercial branding.
Back in the early days of radio (before Congress enacted the Radio Act of 1927), broadcasting was a free-for-all. Domestic frequency assignments were made by the Department of Commerce on a more or less first-come-first-served basis. Many foreign governments didn't even have a mechanism for assigning frequencies; some stations, operating without (or ignoring) governmental authority, simply picked their own frequencies. Even the boundaries of specific "bands" (as we use the term today) weren't uniformly defined. Given the chaotic nature of things, it's not surprising that the Commerce Department didn't assign channel numbers.
The legacy of this chaos lives on to this day: we still use frequency designations in the domestic AM broadcast band and the international shortwave bands.
In order to impose some sort of order on the situation, Congress enacted the Radio Act of 1927, creating the Federal Radio Commission. A few years later, it enacted the Communications Act of 1934, which created the Federal Communications Commission to replace the FRC. Both commissions were charged with responsibility for managing the radio spectrum.
Over the years, the FCC's frequency-assignment policies have evolved into three patterns:
====== ASSIGNMENT by BAND ======
In some bands, the FCC simply assigns the entire band to a specific service, and leaves it up to licensees to assign specific frequencies within the band. Examples of this policy include the amateur radio bands, the common-carrier satellite C- and Ku-bands, and the DBS bands.
====== ASSIGNMENT by FREQUENCY AS CHANNEL NUMBER ======
In some bands, the FCC assigns "channel" numbers to specific frequency blocks, but uses the center frequency of the block as the channel number. Examples:
Radio Control (R/C) Radio Service (47 CFR 95.207):Paging operation (47 CFR 22.531): And even domestic AM Broadcasting: many FCC rules now refer to AM "channels" instead of frequencies, even though the channel number and the center frequency are the same (47 CFR 73.25, -.26, and -.27). ====== ASSIGNMENT by ARBITRARY CHANNEL NUMBER ======
In some bands -- notably FM and TV broadcasting -- the FCC assigns arbitrary channel numbers. These assignments are tabulated in the FCC Rules as follows:
TV broadcasting (47 CFR 73.603):FM broadcasting (47 CFR 73.501): One additional FM Channel (200, at 87.9 MHz) has been assigned since the original assignments were made. It overlaps TV Channel 6; consequently, its use is limited to certain types of stations (see footnote \1\ at 47 CFR 73.501).
Once the FCC finally established television channel assignments, the broadcast and receiver-manufacturing industries adopted them.
But these industries didn't adopt the FM channel assignments. Why not? There's no single reason, but I suspect that it was largely a matter of cultural inertia: broadcasters had been using AM frequency designations for years, and they simply continued the practice with FM.
Furthermore, even by the late 1940s, there was still a lot of confusion about channel assignments (as the aforementioned article by David Ferre makes clear). Receiver manufacturers who had been building FM radios (before channel assignments were finalized) had been using frequency designations by default. Apparently they just continued doing so.
This legacy too lives on to this day: we still use channel numbers for TV and frequency designations (albeit in megahertz rather than megacycles) for FM.
Broadcast stations take these designations very seriously: they've become commercial brand names. AM and FM broadcast stations brand their frequency designations, often with superficial (and not-necessarily-accurate) descriptions: "Nifty Ninety" (really 900); "Super 101" (really 101.3); etc.
Television stations brand their channel numbers: "Local 2"; "Virginia's 13"; "CBS-19"; etc. As brand names, these numbers are so important that many television stations don't even use their actual call signs. Stations even demand that CATV and DBS companies identify them by their channel numbers, even though the actual RF frequencies may be different.
Carrying this branding game to extreme, most television stations plan to continue using their old analog channel numbers as their DTV "channels," even if they move to new channels for DTV. Receiver manufacturers have included mapping logic to display the old numbers. Thus, for example, WISC-TV Channel 3 will become WISC-DT Channel 50, but receivers will display 3.1, 3.2, 3.3, etc. to identify the various video streams.
The FCC also assigns (or accepts ITU assignment of) arbitrary channel designations for certain non-broadcast services. Examples:
Citizens Band Radio Service (47 CFR 95.407):Television Broadcast Auxiliary Service [point-to-point microwave] (47 CFR 74.602): Cable Television Relay Service [point-to-point microwave] (47 CFR 78.18): VHF Marine Channels (ITU RR Appendix S18): Note that the VHF Marine Channels (as mentioned in Michael Quinn's post quoted above) were assigned by the ITU, not the FCC. The FCC incorporates these assignments by reference.