Information about RF propagation and antenna performance doesn't get dated. The physics have been the same since beginning of time. You can use that dated information. What it boils down to are what frequency band you cannot receive properly now with your current antenna. You then focus on a type of antenna that works best for that frequency band. If you are trying to improve all bands then go with that indoor discone solution that jonwienke suggest, if you got room for it.
I use those flat coax for window use but they cut the signal to half at 800Mhz but might still give more signal with an outside the window antenna, if you are allowed to install one.
Remember that receiving simulcast systems could be problematic with a HP-2 scanner, and then you probably need a directional yagi antenna, perhaps attached to your ceiling where it will be out of the way. Those yagis work porly at other frequency ranges than the one they are designed for, but if your lucky you at least will be able to receive some other frequencies better than your stock antenna. There's some $20-$30 yagis so it shouldn't cost too much to try one out.
/Ubbe
