I recently purchased an older Furuno radar with a Si-Tex NavADD 9000 GPS unit. The Si-Tex unit is connected to the radar's CRT screen and acts as a chartplotter when you plug in the C-Map chart cartridges. The only thing I'm missing is the GPS antenna for this machine. I want to use this unit as a back-up to my Garmin chartplotter. Will a generic (non Si-Tex) GPS antenna work with this unit? Could I split the signal on my Garmin antenna to feed the Si-tex unit? I might need an electronics expert for this one. 
Any help will be truly appreciated.
Any help will be truly appreciated.