Testing of GPS units

Weird plugs snipped off. DB-9 soldered to one unit. Tested as follows: GPS 16-HVS RS232 to OpenTracker+ and power from 12V 7AH SLA battery. OT+ plugged into Yaesu VX-3 and same battery. VX-3 plugged into 6V regulator into same battery. Antenna is a modified ¼ wave on a mag base on the cab roof. Modified by applying several layers of heatshrink tubing which electrically lengthens the antenna so I can cut it shorter (by about 20mm or so) and then the top 10% is bent to 90° which makes it short still, without affecting SWR and not having significant affect on radiated power. It still hits my carport, but only just. The VX-3 is on 1.5 watt and (sort of) works around the local vicinity (10 km or so) The GPS and antenna cables are taped to the car and fed through a door on the Trademate. Everything should work better when it's installed properly and a decent transmitter is used. Still debating what radio to use; probably a 5w Chinese cheapie like the Puxing 777 or a Quansheng.