All I can say is welcome to the digital world. There are a million and one reasons why this might be. I recently got into digital scanning and was also frustrated with the lack of consistency on the reception. Since purchasing the right equipment it certainly helped, but still isn't as good as they hype it up to be. As far as not much traffic on the PD, I can believe that. You live in a pretty well behaved city. Many times communications are done over their in car laptop. Spend some time with it on a Friday night or some UWG party night. Also, just because you are next to the PD doesn't mean you are near a tower. OR you could be too close to the tower.
Something I learned quickly about this hobby is that many will tell you why something doesn't work. When it does work, those same people will tell you why it does.
One last thought. The fun of the hobby is figuring it all out. Nobody can tell you the secret recipe because nobody lives where you do with the trees you have with the landscape and other obstructions you have. Be patient, you'll get it.