I have been keeping watch--somewhat erratically--on the Standard-Horizon website, waiting for it to show the GX6000 radio as part of their product line. The GX6000 has finally shown up:
http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&DivisionID=3&ProdCatID=83&ProdID=2858The
owner's manual is also posted and can be downloaded.
Regarding the need for a separate antenna for the radio's AIS receiver, the owner's manual makes this clear on Page 3 under the heading of GENERAL INFORMATION:
The GX6000 has a separate AIS antenna connection to ensure that your will be able to receive AIS signals while transmitting VHF communications.
A few pages later, Page 9, the manual also advises:
The GX6000 require[s] two separate marine VHF antennas; one antenna for VHF and a second antenna for AIS.
On Page 14 a diagram shows the rear panel of the radio. There are two separate SO-239 antenna connectors. The callout for the second connector marked AIS ANT notes:
AIS ANT jack (AIS antenna jack)
Connects an antenna to the AIS receiver. Use a marine VHF antenna with an impedance of 50 ohms.
On Page 18 a diagram of "Electrical Connections" shows two antennas connected, one a "Voice Antenna" and a second an "AIS Antenna."
It seems very clear that a GX6000 radio is going to need a separate, dedicated antenna for its AIS receiver. Recall that
much earlier in this thread, I pointed out this situation.
The purpose of this design seems to be to provide for the possibility that the AIS receiver will be continuously receiving AIS transmissions from other vessels, even while its companion VHF Marine Band radio is transmitting. For that to be workable will require the two antennas to have enough physical separation that the AIS receiver won't be overloaded or desensitized by the transmitter signal from the radio's antenna.
Having a second antenna just for AIS reception, and being able to physically separate that second antenna from the radio's primary antenna, is going to be difficult to accomplish on small boats. For this reason, I don't think the GX6000 is the perfect radio for installation on small boats.