Antenna for ST 6001+ Autopilot

[mphem]

As I brief background, I have a Jeanneau 43DS, located in Kemah. A couple years ago, I installed a C140W and new radome. With help from the forum, I was able to interface all my ST60 instruments. About a year ago, I also installed an AIS, which works great with my C140W. I use the internal GPS antenna for my C140W and have another GPS antenna mounted on the stern railing, with the cable passing though the rail. I'm not sure where the cable ends, but I believe that it goes to my ST 6001+ Autopilot S3G Course Computer. My question is: the old antenna is looking pretty worn (been on boat, probably since 2003) and I just had made a new stainless steel antenna pole, where I have moved the AIS antenna, an iridium antenna and a KVH antenna. I would also like to install a new GPS antenna for the autopilot on the pole. Can someone tell me which antenna I would need to purchase and if I am correct that the rail mounted antenna is for the autopilot. Thanks for the help.
Mike

[Mark - Raymarine - Moderator]

Hello Mphem,
Your S3G autopilot doesn't need a GPS antenna to function, just as your C140W doesn't need an Autopilot to function. They both can work independently of one an another.
As you have already pointed out, the C140W has an internal GPS antenna. In some cases, depending on the location of the MFD individuals would install an external GPS and wire it to the MFD for better satellite acquisition. If your C140W's internal GPS antenna is set to "ON" and is working just fine, then an external antenna is not being utilized / needed, but perhaps for redundancy. Unfortunately, I can only speculate on what the rail mounted GPS is for as we do not know where the GPS wire terminates nor the model number of said GPS.

[mphem]

I guess I will need to crawl below and figure out where the cable goes. I originally thought that it was the GPS antenna for the Pathfinder R70, which I replaced, but then was told it was needed for the autopilot. I have just left it mounted on the rail and it would have remained there, but for my desire to put it on my antenna pole. So I assume from your email, the autopilot is using the same internal antenna as the C140W, if its needs an antenna at all. I guess I could lock in a course and not care the location of the boat? This would make it work independent of the MFD, but the MFD would make the adjustment to get me to a waypoint. I have considered mounting an external antenna for the MFD, but so far I have had no issues with the internal antenna, but now having a good location to mount it above the bimini makes it more appealing.

[Mark - Raymarine - Moderator]

The MFD needs a GPS, the autopilot doesn't. If your MFD is wired to the autopilot, you instruct the mfd to go to a waypoint or follow a route, and that information is passed onto the autopilot and you execute the instructions.