3.579545 MHz Can be More Than the Color Burst

There is a hardly a member of the entire American electronics profession that does not recognize 3.58 MHz as the NTSC* Color Burst standard. This frequency has been the standard for 25 years now, and practically all of us take it for granted that this peculiar frequency is strictly for television operation. As NMOS and the higher density HMOS silicon technology invade the province of Video Display Generation, the 3.58 MHz crystal will have to perform much more than its Color Burst function. In order to generate a video display to a "vanilla" (standard unmodified) television set, four frequencies are required: · VHF (or UHF) Channel Center Frequency The main channel frequency is channel 3 or 4 when generated by an IC Radio Frequency modulator, but may be any channel frequency from 2 through 82. · 3.579545 MHz Color Burst The televisions' color signals ride on the subcarrier that is 3.579545 MHz above the brightness modulated main carrier. Unlike the main channel frequency, the 3.579545 must be a very precise signal. · 6 MHz to 7.5 MHz Dot Clock The dot clock determines how many dots will be generated on a TV screen line. Of course, the more the better. The NTSC* allows only a 6 MHz bandwidth per channel, so the dot clock should be at least 6 MHz. If it does above 7.5 MHz though, the signal may be lost in the traps inside the television set.