关于CATV美国标准

In the US, a TV channel is a 6 MHz wide chunk of bandspace. The bottom edge of the over-the-air channel 2 is 54 MHz and the upper edge is 60 MHz. Within this 6 MHz space is a video carrier, a color carrier, and an audio carrier. The frequency of the video carrier is 1.25 MHz above the lower edge, so for TV Channel 2 the video is at 55.25 MHz. The color carrier is approx. 3.58 MHz above the video carrier (N.B. not the lower edge), so for TV Channel 2 it is 58.83 MHz. The audio carrier is 4.5 MHz above the video carrier, so for TV Channel 2 it is 59.75 MHz. The reason I mention all of this is that you have to be careful to note how a channel frequency is being specified. The two common methods are