Cable pioneer crusading to drive shares of Cablevision higher after trying to take the company private in recent years. Announced $30 million, 10-cent-per-share quarterly dividend in August; mulling more stock buybacks and spinoffs. Market impressed so far; stock up 66% since July low but flat for the year. Family's stake worth $2.4 billion. First attempted to take company private in 2005: initial $7.9 billion eventually swelled to $10.6 billion in 2007; final offer blocked by shareholders. Inventor's son founded network that became Home Box Office. Traded channel with the old Time Inc. for a cable company with 1,500 Long Island customers in 1973. Became Cablevision; today serves 3 million. Company owns Radio City Music Hall, basketball's New York Knicks, hockey's New York Rangers.