Problem with 100Hz TV and Dreamcast

[Estevez]

Tx guyz. OK I have checked it carefully and the problem appears when game runs at 60Hz (so it is almost 90% of games). Do you think that the reason of that may be the connection cable as I am using the regular antenna connection ? Maybe switching to RGB cable will fix it (as when chosing the RGB source in TV there appears the option of switching to NTSC and some other systems, except PAL/SECAM) ? I need to buy such cable anyway.
Tx & keep kewl ;-)