GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Electrical and electronic topics for small boats
Gulfstream
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Joined: Sat Apr 24, 2021 12:12 pm

GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Postby Gulfstream » Sat Apr 24, 2021 12:52 pm

I have attempted to find the answer to my question in past posts on this and other forums but I can't find or I can't understand the exact answer which, I am sure is probably very simple for anyone who actually understands NMEA-0183 TALKERs and LISTENERs

Specifically, I have a Lowrance Gen 3 HDS plotter on which I wish to get DCS and AIS info. Attached to the plotter I have a GX2200 GPS AIS VHF. I do presently have DSC info showing up on the plotter with the basic NMEA-0183 connections of:

VHF TALKER A (gray) CONNECTED TO GPS LISTENER A (orange)
VHF TALKER B (brown) CONNECTED TO GPS LISTENER B (green)
VHF LISTENER A (blue) CONNECTED TO GPS TALKER A (yellow)
VHF LISTENER B (green) CONNECTED TO GPS TALKER B (blue)

Reading up on jimh's many informative postings, I understand that there are two additional talkers (white and yellow) on the VHF that need to be combined with other of the VHF's wiring and connected to the plotters wires to get AIS and DSC info to show on the plotter.

What wires are spliced together to make this magic happen?

ASIDE. I am a new forum participant but a long-time lurker who is appreciative of all the great advice on this forum.

jimh
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Location: Michigan, Lower Peninsula
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Re: GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Postby jimh » Sat Apr 24, 2021 1:36 pm

The problem may be in the configuration of the GX2200. I will refer to the owner's manual. If you don't have one, see

https://www.standardhorizon.com/downloa ... cation/pdf

See section 10.6 NMEA DATA IN/OUT

Read this section carefully.

If you set the the baud rate to 38400 the radio will send both DSC and AIS data on the NMEA-0183 output conductors GRAY (Talker A) and BROWN (Talker B).

IMPORTANT: you must change the baud rate on the chart plotter to also be set to 38400. See your HDS Operator Manual for advice on how to accomplish that. To get the installation manual see

https://softwaredownloads.navico.com/Lo ... -002_w.pdf

See page 44, NETWORK --> NMEA-0183 ---> BAUD RATE for advice on how to configure.

Try that solution and report back if it worked.

The alternative would require that the chart plotter have two NMEA-0183 LISTENER ports (or inputs). But the HDS Gen 3 typically will only have one NMEA-1083 input. The only option with this chart plotter is to set the radio to send both data streams on one port.

PRIMER ON NMEA-0183
It is not possible to WIRE together one LISTENER to get data from two TALKERs. However, the opposite is possible: you can wire one TALKER to send data to two LISTENERs.

Gulfstream
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Joined: Sat Apr 24, 2021 12:12 pm

Re: GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Postby Gulfstream » Sat Apr 24, 2021 3:06 pm

jimh--thank you. Followed your instructions and everything is working--Cheers.

jimh
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Location: Michigan, Lower Peninsula
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Re: GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Postby jimh » Sat Apr 24, 2021 3:49 pm

GULFSTREAM--to hear of a good outcome is always encouraging.

Your initial connections were perfectly correct. The real problem was the separation of the DSC data from the AIS data in the default set-up of the radio.

With regard to NMEA-0183, the default data transmission rate of 4800-bps is too low to be able to transmit all the AIS data that the radio could receive from other vessels if the radio were located in reception range of many other vessels, as might occur in a very busy commercial port. To cram all the AIS data into the bandwidth of 4800-pbs and also add the DSC data would create a situation in which AIS or DSC data might be lost. For that reason, the radio will only combine the two into one data stream if the data transmission rate is increased to 38400-bps. That is why the radio baud rate and the chart plotter baud rate had to be changed to 38400 to accommodate the single data stream.

PRIMER ON BAUD RATE
In data communications the baud rate refers to how often the signal changes per unit of time. To understand this better, think of the signal being a flag raised on a flag pole. If the baud rate were 1-bit per hour, the flag would be changed once every hour and left in place for an hour. With such a low baud rate the chances for an error in transmission of the data is very low. However, even with a low 1-baud rate, it is possible to encode more data into the signal that just one binary bit. Returning to the flag analogy, a 1-bit data payload would be the flag was a uniform color, say black or white.

To understand how more than one-bit of data could be encoded into 1-baud, consider the case where the flag could be constructed with four panels, and each panel could be either white or black. Now each flag change, 1-baud, can encode 4-bits. In a similar manner, using phase shift or frequency shift keying instead of just off-on keying, a radio signal can be modulated to contain more than 1-bit of data in each baud change.

Gulfstream
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Re: GX 2200 Radio to Lowrance HDS Gen 3 Plotter using NMEA-0183

Postby Gulfstream » Sat Apr 24, 2021 8:15 pm

jimh wrote:Your initial connections were perfectly correct.

The reason I had those perfect connections was your tutorial. Thanks again.