DTTB Side Bands
The side bands generated from the spectrum spread or regrowth (from noise or intermod.) may be limited by the “Co - channel” restrictions imposed upon the DTTB to PAL ratio.
As shown the co - channel DTTB to PAL ratio without causing interference is - 45 dB.(flat spectrum across PAL)
As the side bands only need to be down this far, the DTTB to PAL ratio can be deducted from this figure to arrive at the Transmission C/N which will produce PAL interference.
Hence with a DTTB to PAL ratio of 10 dB, the side band level may be - 35 dB. ( ie 35 dB Transmission C/N)
Hence the side band levels are controlled by the DTTB decoding requirements of 43 dB Transmission C/N.