A GPS will only control which systems you receive as you travel if location control is enabled on the scanner. It has absolutely nothing to do with what you are able to receive in your local area if location control is disabled. If the scanner is in ID Scan, try switching to ID Search. It will receive every talkgroup on a trunked system whether it is programmed or not. While scanning the Portland trunked system, press the Scroll knob and then SCAN/SEARCH to toggle between ID Search and ID Scan.