I understand that they used 405 lines for the CBS system so that the signal would fit into the 6mhz channel's that were already in use. What width did the channel have to be to use 525 lines with the CBS system? Understanding of course, that the refresh rate was different and that effects bandwidth usage as well.

David

the exact answer depends on a couple of things. CBS cheated on the horizontal resolution a bit, claiming that color helped distinquish objects, and also that the apparent sharpness would be good enough by using "crispening" techniques. Also, they reduced the frame rate to 24 frames per second (144 fields)

If you suppose 525 lines and 30 complete pictures per second, and the same horizontal resolution as black and white, the field sequential color would require 3 times the bandwidth as 525 black and white. The actual video bandwidth for black and white is 1.25 Mhz for the vestigial lower sideband, and 4.2 MHz for the upper sideband (total 5.45 MHz). The color case could also use 1.25 MHz for the lower sideband, but would need 3 x 4.2 = 12.6 MHz for the upper sideband. If the frame rate was reduced to 24 fps, this upper sideband would be reduced to 10.08 MHz.

DuMont produced some closed-circuit field sequential gear using 3 times the black and white rates.

See: http://www.earlytelevision.org/dumon...ial_color.html