I recently got a Panasonic HDTV set (Tau series. pure flat stereo model) as a gift from someone who already moved out. was wondering if i need a converter box for it to receive digital signals. bought a RCA uhf/vhf/fm stereo indoor antenna and can get only 2 channels clear enough, with a possible 3rd channel (very snowy). all other channels are not coming in. the tv is not on cable mode and i have adjusted the dial on the antenna many times but to no avail. do i need to purchase a stronger antenna, get cable tv, or get a digital converter box? i live in a major us city.