If you have TV/cable leads already installed at or close to where you want to run your scanner coax, you can run the coax down the same way. Remove the wall plate for the antenna connection and disconnect the lead-in. Tie a long cord (have plenty on hand), like package twine, to the lead-in, then go up in the attic where the lead-in runs down through the wall and pull it up. When you have the end, tie another piece of cord to the lead-in, then pull the lead-in and second cord back down through the wall. Now you've got cord that you can use to pull cable up or down through the wall. When you're done, you can pull the cord up into the attic for use if you decide to change cables around. (Make sure, of course, that the other end is secured at the wallplate!)
Mark S.