It does not look like your VHF
has a GPS receiver in it. So splitting the antenna would not work. The VHF does have NMEA
input though and your A65 has NMEA
output so you can easily do what you want.
Page 46 of the Silva manual shows the NMEA connection.
The red wire there (GPS +) is the NMEA input on your VHF.
Your A65 has a NMEA connector on the back. See page 18
Connect the NMEA VE+ OUTPUT on the A65 (pin 3, yellow) to the NMEA INPUT on your radio. You might need to connect the NMEA Grounds on both devices together but it may work without doing that. Just be sure in the A65 you have it set to output NMEA sentences RMA, GGA and GLL if available. You can turn everything else off as the Silva only knows those three sentences.