According to the site above,
10 miles is not much, and haven't yet tested at that distance, but 4times that. Not good enough. But when close to the city, I believe it will be good enough, I've seen reviews using the card with notebooks inside hotels, saying the antenna is good enough for all the local channels.* The WinTV-HVR-950 includes a portable ATSC digital terrestrial antenna, which can be used up to 10 miles from an ATSC transmitter. When using the WInTV-HVR-950 in the home or office, we recommend a high gain roof top ATSC digital antenna.