Garmin GPS Antenna Upgrade Question...

[TugScout]

Hi Gang,

My 2012 R-27 has the existing GPS-17N antenna that came from the factory. Last year I upgraded my chartplotter and this year I plan to add an AIS800 and add a heading sensor.

My question is regarding the antenna. Is there an N2K plug on the bottom of the unit so it can be easily replaced with a new model or is it hardwired and will require running new cable and/or splicing into existing cable?

Also, while I'm thinking of it, my N2K backbone is behind the fridge. Since I'll need to pull it out to install drops for the AIS and heading sensor, I was considering pulling a few more drops just for future expansion. Are there any issues with an N2K drop that isn't connected to anything? My other consideration is just extending the backbone to a different/easier to access location for future use. In that case I would install a "T" and add a terminator plug.

Thanks for the help,

Mark

 

[Wee Venture]

If your R-27 has an autopilot you should already have a heading sensor (fluxgate compass) that will work with your AIS. The Garmin AIS 800 has its own internal gps antenna. But if you want to put an external gps antenna in a better location for reception, my understanding is that you will need a separate dedicated antenna. You will also need a connection to a vhf antenna - either to your existing vhf antenna through a splitter (I believe the Garmin 800 has this built-in) or to a separate dedicated vhf antenna. GPS antennas and VHF antennas both have coax cables that must be connected directly to ports on the device (not through NMEA 2000). Regarding your NMEA 2000 spare drop cables, I believe you can do that no problem as long as you install a terminator at the end of each one, which supplies a proper resistance. When you want to connect a device, you simply unscrew the terminator and connect the cable to your device.

 

[fishheadbarandgrill]

Make sure the AIS 800 is compatible with your current chartplotter. I have a 2011 R29 with the 5215. I was advised not to get the AIS 800 by Garmin Tech Support because, while it may be compatible now, future firmware updates are not guaranteed to to backward compatible to the 5215. So I installed the older AiS 600.

 

[TugScout]

Thanks folks,

Yes, my chartplotter is compatible as I installed a 8612 last year. My current antenna is a N2K based model and transmits data through the N2K network. My understanding that these specific antennas are "active" vs. "passive" antennas. As such, they have their own built-in receivers and then transmit the data over the network cable. a passive antenna would use coax cable to connect to a receiver. The newer Garmin antennas are 32 channel vs. the existing antenna which is 10 or 12 channel.

I appreciate the help.

Mark

 

[ixlr8]

Mark,
As others have indicated, the AIS needs it's own dedicated GPS antenna, it can't use/share an existing GPS antenna, N2K or not. The AIS800 has a built in GPS antenna, but others have found that depending on where the 800 is installed, the internal antenna might not be good enough and you will need to add an external GPS antenna. My dealer put the external AIS GPS antenna for my boat in with the rest of the wiring in the helm... didn't work so well and he had to put the antenna on the roof and run the wiring down to the cave where he installed the AIS. I wish I knew where he routed the wire for the antenna.

 

[Wee Venture]

My current antenna is a N2K based model and transmits data through the N2K network. My understanding that these specific antennas are "active" vs. "passive" antennas. As such, they have their own built-in receivers and then transmit the data over the network cable. a passive antenna would use coax cable to connect to a receiver. The newer Garmin antennas are 32 channel vs. the existing antenna which is 10 or 12 channel.

I appreciate the help.

Mark

As you describe, your “active” antenna is a gps antenna connected directly to a GPS receiver with a NMEA 2000 port, which can then share data with other NMEA 2000 devices, similar to how the Chartplotter, vhf radio, heading sensor and AIS receiver share position, heading and other data. The AIS transponder, however, is by design a GPS receiver in and of itself (as I understand it) and by regulation cannot accept gps position data interpreted by another source. The Garmin GPS 800 does connect to the NMEA 2000 backbone and will communicate with your chartplotter through that means. However, unless there has been some very recent development that I am not aware of, no AIS transponder can receive gps data over the NMEA 2000 network. It must have its own dedicated gps antenna (either internal or external). Some AIS transponders supply power to the gps antenna directly through their external antenna port (at about 3VDC) but the antenna is still just basically sending the raw gps signal down the coax cable to the transponder.

This has been my understanding. Admittedly technology is hard to keep up with. If I am wrong about something here, someone please correct me.

 

[SJI Sailor]

My understanding of the situation matches John & Suzanne's.

When I installed a Garmin AIS 800 in our C30 behind the helm, the unit's internal GPS antenna was not adequately reliable on its own. I added the $60 external Garmin antenna -- and decided to see whether it would work if it were just coiled up in the same cabinet behind the helm. It did -- perfect reception for the past 9 months or so with no need to route to the roof. Obviously this could differ for other boats and situations but was a nice surprise.

A couple of notes on the AIS 800. It required a Windows laptop and a long USB A cable to program the first time (I don't recall exactly why -- maybe to add the MMSI, if the dealer hadn't done that). I had to add a connector to the NMEA bus (make sure you have one open or have room to add). And whenever I update Garmin software, it goes offline -- but that is easy to fix by pulling the fuse to reboot it.

One small thing I really like is to check on her occasionally on the Marine Traffic app. Nice to know that she's in the right place and with power.