North American television frequencies

North American television frequencies are different for over-the-air (also called terrestrial) and cable television systems. Over-the-air 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 83 and occupies frequencies between 470 and 890 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 change was the deletion of channel 1, originally intended as a community channel and the spectrum given to two-way land-mobile radio.[1]

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 broadcast band when the digital television 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]

Wireless microphones and medicaltelemetry devices formerly shared some of the TV bands, but transmitted at a very low power. After the migration of digital television in 2009, the Federal Communications Commission (FCC) banned these from using the 700 MHz band in the U.S., effective June 12, 2010. The 700 MHz band is now used for public safety communications and wireless broadband providers.[4]

The following table lists over-the-air television channels in the ultra high frequency band. Some entries have a colored background, indicating that the channels have been reallocated for other use. The notes below the table explain the re-allocations.

With the advent of digital television in 2009, stations are allowed to identify themselves by a virtual channel that may not necessarily be the same as the station's RF channel. Virtual channels 1, 37, and 70 to 99 can be assigned via PSIP even though there is no corresponding physical station on that RF channel.[7]

"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 RF 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 TV network.[9] The IRC plan attempts to minimize distortion products by deriving all video carrier signals from a common source.[10] The IRC system assigns channel frequencies (for the North 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.[11]