GPS Antenna Quandary

N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
Hunter Family, assistance requested please.

I think I may have to replace the RS120 GPS antenna with an RS125 version.
  1. Who's done it????
  2. How did you do it???
  3. Did you use the RS120 cable to pull the new RS125 cable through the arch??
  4. Where on earth does that cable run? My current puck is on the SBD davit top which is factory integral to the stainless steel arch.......
  5. How does the signal get to the (in my case) C80 MFD at the helm station.....Seatalk???
Hair is being pulled out.....


Neil
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,516
CAL 35 Cruiser #21 moored EVERETT WA
Hi Neil.
Sounds like you’re in the thick of a project.
I am curious why you are going to use a RS125. The current Raymarine products are the RS150 (flat pancake), the GA200 and the RS 130 (which look like a mushrooms).

Are you installing a new chart plotter? Did the other unit fail?

It would seem usual to be able to use the old cable as a messenger cord. Should work unless the installer used some sort of wire tying plan. This would have been the dealer who commissioned the boat or a previoous owner, not the Hunter manufacturing plant.
 
N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
jssailem said:
Hi Neil.
Sounds like you’re in the thick of a project.
I am curious why you are going to use a RS125. The current Raymarine products are the RS150 (flat pancake), the GA200 and the RS 130 (which look like a mushrooms).

Are you installing a new chart plotter? Did the other unit fail?

It would seem usual to be able to use the old cable as a messenger cord. Should work unless the installer used some sort of wire tying plan. This would have been the dealer who commissioned the boat or a previoous owner, not the Hunter manufacturing plant.
Click to expand

Thanks for the reply John.

My C80 is working fine, although the date is locked in 2005, probably due to the antenna. I thought the 125 would be a good enough upgrade so I didn't have to install a backbone and Seatalk - Seatalkng bridge. My local electronics guru suggested it, and he's been spot on up to now.

I am going back to the boat tomorrow to see if I can trace the cable somehow, but I share your concern there may be a cable tying system in place preventing me from using it as a tail.

Do you happen to know how the current antenna would be connected to the C80? It's certainly not NMEA0183, as I am using that for AIS installation. I have to presume it connects with the small push on fittings on one of the instruments (not the autoplitot) and then goes to the C80 through seatalk connections.

Neil
 
M

MFD

.
Jun 23, 2016
134
Hunter 41DS Poulsbo WA USA
Not sure what the issue is with your RS120, but I am pretty sure they have a battery inside that can die after 10 years or something.
One of those lithium hockey puck type batteries.
 
Davidasailor26

Davidasailor26

.
May 17, 2004
5,493
Beneteau Oceanis 37 Havre de Grace
GPS counts time within “epochs” - basically sets of 1024 week blocks of time through which the the GPS system increments. Older receivers receive the “current” date and assume that it must be 2005, because that was the date when the week counter matched what it’s receiving in the epoch it knows about. A quick Google suggests that the RS120 was never updated for the latest epoch (which started in 2019), but that the RS125 may have been. The 125 is still a very old and unsupported model so depending on whether the one you buy received the update you may still have challenges.
 
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marcham

marcham

.
Jun 17, 2022
170
Hunter 380 Comox BC
RS125 had it's own list of issues.... you probably won't get an accurate date with that one either. I'm just about to replace my 2002 vintage Raymarine GPS receiver (RS 12??) with a Garmin 24XD hooked up to my STNG / ST1 hybrid network. It's relatively affordable and has the added benefit of providing magnetic heading.

Why not just update with an NMEA 2000 GPS and then use a STNG-ST1 converter to hook it up to your ST1 instruments and plotter ? The new receivers are really really good, even through a layer of fiberglass. So an option would be to leave your current antenna or remove/cut and seal the hole, then mount a new GPS in a more convenient area, could be in a lazarette, locker inside, etc....

It will most likely not be a straight pull. You'll need to open every access port in between the current antenna and wherever it connects to the plotter/ST1 network.
 
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M

MFD

.
Jun 23, 2016
134
Hunter 41DS Poulsbo WA USA
I have a C120 plotter and one of the old RS12x (0 or 5, can't recall).
It only feeds the C120, nothing else. I have an entirely separate/duplicate system that is newer.
With the bad battery in the RS12x, and if shutdown for a long time, it will take 10-15 minutes to get a fix. My understanding is from the bad battery. Basically it has no starting reference point from last time it was running to help get a fix faster.
I bought a replacement battery a couple years ago but it ended going into my car key fob after sitting around for a couple months.

Anyway - if I was going to go through the effort to pull wire and replace the RS12x, I would definitely go with something new/modern for sure.
 
N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
marcham said:
RS125 had it's own list of issues.... you probably won't get an accurate date with that one either. I'm just about to replace my 2002 vintage Raymarine GPS receiver (RS 12??) with a Garmin 24XD hooked up to my STNG / ST1 hybrid network. It's relatively affordable and has the added benefit of providing magnetic heading.

Why not just update with an NMEA 2000 GPS and then use a STNG-ST1 converter to hook it up to your ST1 instruments and plotter ? The new receivers are really really good, even through a layer of fiberglass. So an option would be to leave your current antenna or remove/cut and seal the hole, then mount a new GPS in a more convenient area, could be in a lazarette, locker inside, etc....

It will most likely not be a straight pull. You'll need to open every access port in between the current antenna and wherever it connects to the plotter/ST1 network.
Click to expand
Thanks Marcham...I think I have a conversion kit on the boat when I was toying with the idea of connecting a Garmin 74CVX CP to my Seatalk network as a back up plotter.....that might be the way to go ...
 
N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
MFD said:
I have a C120 plotter and one of the old RS12x (0 or 5, can't recall).
It only feeds the C120, nothing else. I have an entirely separate/duplicate system that is newer.
With the bad battery in the RS12x, and if shutdown for a long time, it will take 10-15 minutes to get a fix. My understanding is from the bad battery. Basically it has no starting reference point from last time it was running to help get a fix faster.
I bought a replacement battery a couple years ago but it ended going into my car key fob after sitting around for a couple months.

Anyway - if I was going to go through the effort to pull wire and replace the RS12x, I would definitely go with something new/modern for sure.
Click to expand
Thanks MFD, I think you and Marcham are right
 
N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
nhodgson said:
Thanks MFD, I think you and Marcham are right
Click to expand
What I may do is in stall my Em Trak B954 and see if it sends sentences (it has its own internal GPS)
MFD said:
I have a C120 plotter and one of the old RS12x (0 or 5, can't recall).
It only feeds the C120, nothing else. I have an entirely separate/duplicate system that is newer.
With the bad battery in the RS12x, and if shutdown for a long time, it will take 10-15 minutes to get a fix. My understanding is from the bad battery. Basically it has no starting reference point from last time it was running to help get a fix faster.
I bought a replacement battery a couple years ago but it ended going into my car key fob after sitting around for a couple months.

Anyway - if I was going to go through the effort to pull wire and replace the RS12x, I would definitely go with something new/modern for sure.
Click to expand
I may see if when I connect my Em Tral B954 AIS (it has its own internal gps) to the the MFD via NMEA0183 fit sends the sentences to it first before I go to the point of replacement
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,516
CAL 35 Cruiser #21 moored EVERETT WA
nhodgson said:
I may see if when I connect my Em Tral B954 AIS (it has its own internal gps) to the the MFD via NMEA0183 fit sends the sentences to it first before I go to the point of replacement
Click to expand
A great idea.
I looked up the C80 install manual. The RS120 was connected to Seatalk backbone. It appears sending NMEA0183 data to connected listeners.
 
N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
jssailem said:
A great idea.
I looked up the C80 install manual. The RS120 was connected to Seatalk backbone. It appears sending NMEA0183 data to connected listeners.
Click to expand
....I'd probably need to disconnect the RS120 too wouldn't I? Unless it takes whatever gps data it can from multiple sources....I don't see how it wouldn't work....
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,516
CAL 35 Cruiser #21 moored EVERETT WA
Sounds good. Test and Verify. The unit is either transmitting GPS strings on the network or it is not. Do you have a way of reading the data?

Here is a link to help decode the data.

NMEA-0183 messages: Overview

receiverhelp.trimble.com receiverhelp.trimble.com
 
marcham

marcham

.
Jun 17, 2022
170
Hunter 380 Comox BC
nhodgson said:
What I may do is in stall my Em Trak B954 and see if it sends sentences (it has its own internal GPS)


I may see if when I connect my Em Tral B954 AIS (it has its own internal gps) to the the MFD via NMEA0183 fit sends the sentences to it first before I go to the point of replacement
Click to expand
If you update one of the settings via the app, the Emtrak will broadcast the GPS position to the network. However, I am not convinced it broadcasts all the quality of signal details that chartplotters usually require.... worth a try. It works as the GPS source for Navionics / Aquamap.
 
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DRhoads

DRhoads

.
Apr 12, 2007
200
Hunter 420 Herrington Harbor South
From the original question see below in red_ish.

I think I may have to replace the RS120 GPS antenna with an RS125 version.
Who's done it???? Yes, have done it
How did you do it??? Removed the old unit and replaced with a 125 same spot, same connections, same cable
Did you use the RS120 cable to pull the new RS125 cable through the arch?? N/A
Where on earth does that cable run? My current puck is on the SBD davit top which is factory integral to the stainless steel arch.......
How does the signal get to the (in my case) C80 MFD at the helm station.....Seatalk??? Yes, most likely just as it did before.

The 120 has a soldered battery. You can break the solder and replace the battery (most likely the failure) and retack. On the 125 you can unscrew the back and replace the battery. Simple and works. I have replaced the battery twice. I still have the old ST1 system of instruments and plotter (L1250+) and they keep on working
:)
(so far)
 
Last edited:
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N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
DRhoads said:
From the original question see below in red_ish.

I think I may have to replace the RS120 GPS antenna with an RS125 version.
Who's done it???? Yes, have done it
How did you do it??? Removed the old unit and replaced with a 125 same spot, same connections, same cable
Did you use the RS120 cable to pull the new RS125 cable through the arch?? N/A
Where on earth does that cable run? My current puck is on the SBD davit top which is factory integral to the stainless steel arch.......
How does the signal get to the (in my case) C80 MFD at the helm station.....Seatalk??? Yes, most likely just as it did before.

The 120 has a soldered battery. You can break the solder and replace the battery (most likely the failure) and retack. On the 125 you can unscrew the back and replace the battery. Simple and works. I have replaced the battery twice. I still have the old ST1 system of instruments and plotter (L1250+) and they keep on working View attachment 229633 (so far)
Click to expand
I wonder if this has anything to do with the gps losing a fix here and there.....
 

Attachments

N

nhodgson

.
Nov 9, 2023
15
Hunter 36 Merritt Island
nhodgson said:
....I'd probably need to disconnect the RS120 too wouldn't I? Unless it takes whatever gps data it can from multiple sources....I don't see how it wouldn't work....
Click to expand
The 120 has a soldered battery. You can break the solder and replace the battery (most likely the failure) and retack. On the 125 you can unscrew the back and replace the battery. Simple and works. I have replaced the battery twice. I still have the old ST1 system of instruments and plotter (L1250+) and they keep on working View attachment 229633 (so far)
[/QUOTE]

I wonder if this has anything to do with the gps losing a fix here and there.....

The pic was snapped as found while tidying up AIS and instrument cables
1738794820214.png


1738794820214.png
IMG_1746.JPEG
 
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