Analog Channels
For analog TV stations the FM audio carrier is 4.5 MHz above the 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. On many FM radios, the audio for analog channel 6 can 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. Digital channel 6 cannot be decoded on an analog radio, and often DTV channels reside on a different channel than the one they advertise.
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.
Read more about this topic: North American Broadcast Television Frequencies
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