Antenna placement and coax length could be playing a part as well. The dinky little antennas that ship with the rtl dongles aren't terrible but setting one up indoors and probably next to or on top of a pc that's spewing all sorts of noise could dramatically affect reception. Also if you're connecting your antenna through a coax cable that's rolled up into a coil it can affect your signal. if your coax is too long, dont coil it up. Just stretch out the excess.