The North American broadcast television frequencies are on designated television channels numbered 2 through 69, approximately between 54 and 806 MHz. Traditionally, the frequencies are divided into two sections, the very high frequency (VHF) band and the ultra high frequency (UHF) band. The VHF band is further subdivided into two more sections, VHF-Lo (band I) and VHF-Hi (band III). In between lie allocations for other services including the FM broadcast band (band II), bands used for land mobile radio, radio remote control, civil service agencies, amateur radio, and aircraft navigation aids and voice communication (airband).

On many FM radios, the audio for channel 6 can often be picked-up by turning the tuner dial below the lower FM band edge, at 87.75. The volume is low as the frequency deviation for TV audio is only ±25 kHz, versus ±75 kHz for FM broadcasting. The lower sideband of HD Radio signals on 88.1 also overlap slightly from 87.9 to 88.0.

The FM audio carrier is 4.5 MHz above the VSB video carrier, and the total channel bandwidth is 6 MHz. The video carrier is nominally 1.25 MHz above the lower channel edge. In some cases, analog TV stations are assigned carrier frequency offsets of +10 or −10 kHz to minimize RF interference with distant stations on the same channel (see NTSC for more details). Positive-offset station will therefore end in .26, while negative-offset stations will end in .24, and are usually denoted with a plus or minus sign immediately after the number (such as 8⁺ or 37⁻). While offsets are rare in digital TV, positive-offset stations end in .3380556, while non-offset stations end in .30944056 (rounded to .31).

Analog stations must be separated by at least one unused channel except for non-adjacent channel pairs 4 and 5, 6 and 7, and 13 and 14.

Wireless microphones and medical telemetry devices already share some of the TV bands, but transmit at a very low power. In early 2010 the Federal Communications Commission (FCC) banned these from using the 700 MHz band in the U.S., effective June 12.^{[citation needed]}

Changes and variations

Channel 1 was removed early on as a community television reservation and given to amateur radio and other uses. Channels 70 through 83 were removed from the bandplan in the 1980s to make way for AMPS mobile phone service. These channels were mainly used in the U.S., and mainly for broadcast translators, some of which continued in operation if their frequencies were not used by cellular. Channel 37 is allocated to radio astronomy and may not be used by any station.

In the U.S., channels 52 through 69 are being reallocated for other purposes as the transition to digital television broadcasting is completed for low-power TV stations. All full-power analog broadcasts ended in June 2009, and all temporary full-power digital broadcasts moved back down to the lower channels. While most other countries abandoned VHF due to its poor suitability for TV broadcasting and allocation for Digital Audio Broadcasting, the FCC chose to cut high-UHF channels instead, because frequency-use rights could be auctioned for a greater price.^{[citation needed]}

Channels 14 through 19 are used for two-way radio in major cities on a non-interference basis, although the transition to digital television (DTV) has caused problems in certain instances when a previously unused channel has begun to be used for DTV broadcasts. The same holds true for wireless microphones and medical telemetry devices in that band.

In most regions, new digital television stations are placed on UHF (14 to 51, except 37 and sometimes 14 and 20) or high-VHF channels (7-13), although others are used in some of the more crowded media markets. With virtual channel numbering, many digital televisions group digital channels with their corresponding analog broadcasts. For example, the first digital TV stream of a station that broadcasts analog TV on channel 4 will usually appear as 4-1 or 4.1 on a DTV receiver, even though the digital transmissions may be on channel 38. Several digital subchannels can be multiplexed together, so 4-1 through 4-5 might be used by one station. Subchannel 0 (e.g., 4-0) designates the analog broadcast. In the U.S., all channels from 7-36 and 38-51 are frequently used for digital TV broadcasts. However, VHF 2 to 6 are rarely used by DTV broadcasters due to ongoing problems with impulse noise, and channel 6 being an adjacent channel to the FM broadcast band. Additionally, VHF performance is poor for mobile TV, with ATSC-M/H being the standard finalized and approved in late 2009.

The VHF bandplan was modified several times before 1948. The last change was the transfer of channel 1, originally intended as a low-power (less than 1,000 watts) LPTV community channel, to two-way land-mobile radio and the six-meter amateur radio band. [1] Amateur television (ATV) is used on four channels in the 420-450 MHz (70-centimeter) amateur band; UHF TV channel 14 starts at 470 MHz. These ATV channels are popular for repeater output and direct communications and are seen over-the-air with a cable-ready tuner set to channels 57 to 60 (14 being seen on 65). ATV is also used on the other amateur bands above 450 MHz. ATV is also known as HAM TV or Fast Scan TV.

VHF bands

Note the upper edge of analog TV 6 slightly overlaps FM channel 200, 87.9 MHz. That FM frequency is used by KSFH, various low power pirate stations, and broadcast translator station K200AA (the only USA repeater licensed to use that frequency).
Analog TV 6 audio can be heard on 87.7 or 87.8, but with lower sound volume and therefore fidelity due to differences in the FM specifications between TV and FM radio. Some low-power analog TV stations (see here) operate on TV 6 with the intent of being heard on FM radio at 87.7 MHz.

UHF band

In the United States, channels 52 to 68 have been reallocated to Part 90 Land Mobile Radio Service. Channels 70 to 83 were previously reallocated to Land Mobile Radio Service and Cellular Mobile Radio Service in 1982. 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 in these countries.

Notes

• Virtual channels 1, 37, and 70 to 99 can be assigned via PSIP even though there is no corresponding physical station on that channel.

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

See also

External links

• 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
• U.S. cable television channel frequencies
• TVTower.com - Commercial Television Frequencies