winfast dtv2000

I have one of these winfast dtv cards, When I try to record from a digital channel the file is recorded to where i want but it uses 1mb per second, so to record a half hour tv show it would use 1.8 gb is there anyway to make it record at an aceptable level, or would I have to convert it after it has recorded. the only option for recording is .mpg, format.