The answer is to use an active (ie amplified) aerial - the older GPS units tend to be a bit 'deaf' compared with the newer technologies. The GPS 195 has 5 volts available on its aerial socket and this supply powers the amplifier in the antenna.
Have a look for a Garmin GA27 remote aerial on eBay (mine cost about £15), mount it with as good a view of the sky (normally well forward on the 'dash' at the bottom of the screen) and you should lose the 'poor signal' warning!