Charles F. Dolan, the 78-year-old chairman and controlling shareholder of Cablevision Systems, does not give up easily. Yesterday he said that he was forming a company to buy the remaining assets of Voom, the troubled satellite company that the Cablevision board decided to sell to EchoStar Communications last month over Mr. Dolan's objections. During the Cablevision board battle over Voom, one of Mr. Dolan's sons, Thomas, sided with his father against another son, 49-year-old James, who is Cablevision's chief executive. Thomas C. Dolan, the executive vice president of Cablevision, and his father will be part of the new company, which will be called Voom HD. With yesterday's development some investors and analysts wondered whether Charles Dolan would sell some or all of his family's holdings in Cablevision to finance the venture. Mr. Dolan was not available for comment.