I need some advice. I just bought my Sprint PCS Novatel Merlin S620 EV-DO card today. I found a place on the web to buy the external antenna cables and antennas, however I am not sure how to go about choosing an antenna for my card. Beside being EV-DO compatible what else should I be looking for to give me the best distance and performance. Or do they make a big enough difference to even bother with them?