[C320-list] External GPS antenna wire routing and NMEA 0183 question

[Stephen Cox]

> 
> I am about to install my AIS, at long last. I purchased the 
> XB8000 that requires an external GPS antenna. My question is 
> this - is there a reason that I should not simply pass the 
> GPS antenna cable through one of the two cowlings on the 
> stern of the boat and utilize one of the two large holes that 
> are already cut? Or should I buy a waterproof cable gland/sea 
> strut and pass through the deck/transom? If the latter, is 
> there a preferred location? My plan is to zip-tie it to the 
> railing until I get to the point of ingress on the boat.  
> 
> Also, I plan to connect the NMEA 0183 listen from the chart 
> plotter to the NMEA 0183 talk from the AIS. I plan to leave 
> the NMEA 0183 talk from the chart plotter connected to the 
> VHF for my DSC. I think this will work, but I am not sure if 
> I need to connect the NMEA 0183 listen for the AIS. I think I 
> could run my NMEA 0183 Wind and Depth to the AIS and then the 
> AIS would also communicate that to the chart plotter, but I am 
> not sure. If anyone has any thoughts about this configuration 
> besides converting to NMEA 2000 (everything on the boat is 
> NMEA 0183 so I am not converting it all to NMEA 2000 right 
> now), that might save me lots of trial-and-error.
> 

On my AIS (not a Vesper) the provided GPS antenna was not an external one as such.  I mounted it behind the panel the AIS was
mounted to, underneath the deck, and it receives the required signal just fine.  You may not need to run yours externally, at least
while you are setting it up initially.  I do have a Raymarine RS125 external GPS aerial mounted on the pushpit railing and I ran the
cable for that internally to the railing.  I used the hole through the deck and the base of one of the pushpit uprights used for one
of the external stereo radio speakers so I didn't have to drill any additional holes in the deck.  I did need to enlarge the
existing hole though which was a bit tricky, given the speaker wire was already there.  I used a small round file to carefully
enlarge the deck and pushpit holes sufficient to get the wire through.  I did have to drill a hole in the rail to get the wire out
and I did that underneath the top horizontal rail close to the vertical part of the rail.  Don't forget to use a grommet here to
protect the cable.

Your proposed NMEA 0183 wiring is basically how mine is wired and should be fine.  Just make sure you set the baud rate correctly on
each leg.  The AIS talk output to the chart plotter is typically run at the 38400 Baud rate while the talk output from the chart
plotter to the VHF is more likely to require to be 4800 baud. You should not need an NMEA 0183 listen signal to the AIS for it to
function, although as you say, it could be used a way to pass on your other instrument outputs if they are not already going to the
chart plotter.  This listen signal would need to go into the 4800 baud input wire.

Hope this helps,

Stephen Cox
Tegwen #1141