I know I am replying late, and may have missed some of this in the previous replies from Dewey and Upman, but I suggest you start with the online user guide for the HP-1 on Uniden's Twiki site and/or http://marksscanners.com/HP/HP.shtml . Specifically, read up on favorites lists and the selections for each list in Sentinel that turns on/off Monitoring, Downloading, Location selection.
You can load the HP with fav's for a road trip of just what you want to hear, and turning on the locations, your GPS will turn them on/off as you pass into the preset range of each system. You can sort of do the same using the main database and service selections, but with less control.
As far as the garmin GPS, be sure it does output NMEA to the cable you are using. Most newer stand alone GPS by Garmin no longer output data. My biggest (maybe ONLY) complaint with the Uniden "puck" GPS is that it needs a second power source. I was hoping the new 436HP would address that, but "sigh" no such luck!
Joel R Kahn
From: "gclaridge@..." To: HomePatrol@... Sent: Thursday, February 13, 2014 10:47 AM Subject: [HomePatrol] Home Patrol and GPS
Hello group;
I am a new Home Patrol user and will be connecting a Garmin GPS unit to it while mobile. Should I remove all my favorites from the Home Patrol and rely on the GPS to find local frequencies? I believe I have to set up the service types I am interested in, but I don't think I need any favorites.