The Pan-American television frequencies are different for terrestrial and cable television systems. Terrestrial television channels are divided into two bands: the VHF band which comprises channels 2 through 13 and occupies frequencies between 54 and 216 MHz, and the UHF band, which comprises channels 14 through 36 and occupies frequencies between 470 and 608 MHz. These bands are different enough in frequency that they often require separate antennas to receive (although many antennas cover both VHF and UHF), and separate tuning controls on the television set. The VHF band is further divided into two frequency ranges: VHF low band (Band I) between 54 and 88 MHz, containing channels 2 through 6, and VHF high band (Band III) between 174 and 216 MHz, containing channels 7 through 13. The wide spacing between these frequency bands is responsible for the complicated design of rooftop TV antennas. The UHF band has higher noise and greater attenuation, so higher gain antennas are often required for UHF.
The VHF band plan was modified several times before 1948. The last of these changes was the deletion of channel 1, originally intended as a community channel. This allocation of the spectrum was given to two-way land-mobile radio.[1]
UHF channels 70–83 in the United States were reallocated in 1983.
In March 2008, the FCC requested public comment on turning the bandwidth currently occupied by analog television channels 5 and 6 (76–88 MHz) over to extending the FM terrestrial band when the DTT transition was to be completed in February 2009 (ultimately delayed to June 2009).[2] This proposed allocation would effectively assign frequencies corresponding to the existing Japanese FM radio service (which begins at 76 MHz) for use as an extension to the existing North American FM broadcast band.[3] [needs update]
The UHF 700 MHz band comprised the spectrum of UHF channels 52 through 69. Channels 52–69 are no longer available for normal, high-power digital terrestrial television broadcasting in the United States, but some channels are available for use as low-power or translator stations.[4] Wireless microphones and medical telemetry devices shared some of the space on this television band, if transmitting at a very low power. After the migration to digital terrestrial television in 2009, the Federal Communications Commission (FCC) banned all of these from using the 700 MHz band, effective June 12, 2010. The 700 MHz band is now used for public safety communications and wireless broadband providers.[5]
In 2017 the FCC auctioned off all remaining UHF spectrum including and above UHF channel 38.[6] This required the reconfiguration of channel allotment (known in the terrestrial television industry as the channel "repack"), allowing for higher gain small antennas to cover a smaller frequency range. In April 2017 it was decided that channels 38 to 51 would be deleted, but channel 37 remains reserved. Channel repacking proceeded in 10 phases from September 2018 through July 2020.[7]
The following table lists terrestrial television channels in the ultra high frequency band as they were allocated in their modern form by the Federal Communications Commission on April 11, 1952. The original allocation included 70 UHF channels (14–83) with 6 MHz separation. In the decades since, many of the channels have been de-allocated and reserved for other purposes. Channels 14–36 are usable UHF channels in the United States after the most recent change was completed in 2020. Formerly allocated channels are indicated with a colored background, and their dispositions are explained in the notes below the table.
Harmonically-related carriers (HRC) is a system for assigning television channel numbers to bands of frequencies over a cable television network.[citation needed] William Grant, in his book,[11] states:
"By harmonically relating the carrier frequencies themselves it is … possible to improve system performance. This does not reduce the beats produced, but positions them within the system transmission spectrum, such that they are more tolerable. In effect, all signal carriers are spaced precisely at 6 MHz apart, and thus, all beats generated are at 6 MHz increments.Since the television signals are vestigial sideband modulation, if the beat products can be manipulated to fall on or near the Radio frequency carriers themselves, they are much less offensive."
Incrementally-related carriers (IRC) is a system for assigning television channel numbers to bands of frequencies over a cable television network.[citation needed] The IRC plan attempts to minimize distortion products by deriving all video carrier signals from a common source.[12] The IRC system assigns channel frequencies (for the Pan-American NTSC-M system) spaced 6 MHz apart. In an IRC system, the VHF channels are at their off-air frequencies except for channels 5 and 6, which will be 2 MHz higher than usual.[13]
Both HRC and IRC systems have the added advantage of allowing for one extra channel to be positioned between channels four and five, as the gap between them increases from 4 MHz wide to 6 MHz wide. It is often mapped as channel one or channels 2, 3, and 4 become channels 1, 2, and 3, and the new one becomes channel 5.
These frequencies are used for both NTSC-based analog television and QAM-based digital television. Band plans for Pan-American American cable television systems are standardized in EIA standard 542-B.[14]
Channels 57 to 61, and 143 to 145, are used in amateur television.
Cable channels 98 and 99 (A2 and A1, 108-120 MHz), if used, have appeared as channel 00 and 01 respectively on some cable boxes.[15]
Certain commenters have urged the Commission to give a "hard look" to a proposal that the Commission re-allocate TV Channels 5 and 6 for FM broadcasting73 FR 28400, 73 FR 28403