Scanner Antenna Upgrade for Home? - Trains Magazine

Lot's of options on-line, and you can easily go 50-100' with coax.

Check for local radio shops - they may have something useful for you. If all you are listening to is railroad, you can settle for a VHF-High antenna - otherwise you may want to look for a multi-band antenna.  (Phoenix Fire was still running on VHF-Hi last I knew - don't know about the Police...)

Failing a radio shop, stop by your local Radio Shack.  They still have some antennas and definitely have coax - already terminated on both ends if you aren't handy with doing that yourself.  You might have to pick up an adapter for your radio, too.

Once you've got your antenna, you've got to get it mounted.  Once again, wherever you get the antenna should also have some mounting options.  Altitude is important - the higher you get the antenna, the more you'll pick up.  Consider local conditions, though, as you can stick an antenna pretty high in calm winds, but it won't last long with a stiff breeze or worse.  Guy wires would become important, or a pretty secure tripod base. 

Consider where you will mount the antenna before you buy the coax, too.  It wouldn't be pleasant to get 50' only to discover you need 100' - and after you run it hither and yon to get from the antenna to where you plan to have  your scanner, the distance can add up.

There is a trade-off between the gain achieved by elevating the antenna ever higher and the cost to do so. You have to decide what that is.

Make sure you don't run afoul of any building codes, etc...