The PAL subcarrier frequency is 4.43361875 MHz. This is derived from 284 subcarrier cycles, or dots, in each line period. This would give about 231 visible dots on each picture line - the active line period. They would all be stationary (in the same position in each frame and field) ,and all in the same position on each horizontal picture scanning line, forming a highly visible static pattern of vertical stripes. Offsets are added to make these lines move, and tilt them over diagonally. The quarter line offset means 283.75 cycles per line, one quarter of a cycle less on each line. The only other offset is the 25Hz offset, which means one more cycle per frame of 625 lines, i.e. 0.0016 extra cycles per line. Hence the actual number of subcarrier cycles per line 283.7516 This is why the PAL subcarrier frequency is what it is. Multiply the number by 625, the number of lines in a frame, and then by 25, the number of frames in a second, and it comes to the number of subcarrier cycles per second, 4,433,618.75