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 - 6, and VHF high band (Band III) between 174 and 216 MHz, containing channels 7 - 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.

Broadcast television

History

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]

700 MHz band

Wireless microphones and medical telemetry 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]

Channel frequencies

VHF band

NOTE: ATSC pilot signal approximately 310 KHz above lower edge.

UHF band

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.

Notes

• Channel 37 is reserved for radio astronomy in the United States, Canada, Bermuda and the Bahamas, thus there are no television stations assigned to it. Mexico also informally observes a ban on transmitters using this channel.
• On August 22, 2011, the United States' Federal Communications Commission announced a freeze on all future applications for broadcast stations requesting to use channel 51,^[5] to prevent adjacent-channel interference to the A-Block of the 700 MHz band. Later that year (on December 16, 2011), Industry Canada and the CRTC followed suit in placing a moratorium on future television stations using Channel 51 for broadcast use for the same reason.^[6]
• Channels 52 through 69 in the United States have been reallocated now that conversion to digital TV was completed on June 12, 2009.
• The frequencies used by UHF channels 70 through 83 were reallocated to the Land Mobile Radio System (Public Safety and Trunked Radio) and mobile phones in a CCIR worldwide convention in 1983.
• 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]

Cable television frequency issues

• UHF channels 14 to 43 translate to common cable-ready channels 65 to 94 (add 51).
• UHF channels 44 to 69 translate to rarely used cable TV channels 100 to 125 (add 56).

Historical band plans

Cable television

Harmonically related carriers (HRC)

Harmonically related carriers (HRC) is a system for assigning television channel numbers to bands of frequencies over a cable TV network.

William Grant, in his book,^[8] 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 RF carriers themselves, they are much less offensive."

Incrementally-related carriers (IRC)

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 (Incrementally Related Carrier) 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]

Channel frequencies

These frequencies are used for both NTSC-based analog television and QAM-based digital television. Band plans for North American cable television systems are standardized in EIA standard 542-B.^[12]

Channels 57 to 61, and 143 to 145, are used in Amateur Television.

NOTE: Frequencies given are for luminance carriers. For channel center frequencies, add 1.75 MHz.

Channel usage

Cable channels 98 and 99 (A2 and A1, 108-120 MHz), if used, have appeared as channel 00 and 01 respectively on some converter boxes.^[13]

See also

• Australasian television frequencies
• Broadcast television systems, including:
  • Advanced Television Systems Committee standards
  • DVB
  • Multichannel television sound
  • NTSC
  • NTSC-J
  • PAL
  • RCA
  • SECAM
• Early television stations
• European cable television frequencies
• Knife-edge effect
• Moving image formats
• Multichannel television sound
• Television channel frequencies
• Ultra high frequency
• Very high frequency

References

External links

• HRC
• ARRL - TV Channel, CATV and FM Broadcast Frequencies by Kevin K. Custer (W3KKC)
• U.S. cable television channel frequencies
• TVTower.com - Commercial Television Frequencies
• What ever happened to Channel 1? - J. W. Reiser, based on a Radio-Electronics article of the same name by David A. Ferre.
• Post-transition U.S. digital TV channel assignments as of 1 August 2007