 DuMont survived the early 1950s only because of WDTV in Pittsburgh , the lone commercial VHF station in what was then the sixth @-@ largest market . WDTV 's only competition came from UHF stations and distant stations from <unk> , Pennsylvania ; <unk> , Ohio ; and <unk> , West Virginia . No other commercial VHF station signed on in Pittsburgh until 1957 , giving WDTV a de facto monopoly on television in the area . Since WDTV carried secondary affiliations with the other three networks , DuMont used this as a <unk> chip to get its programs cleared in other large markets . 
