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Author Topic:   Connecting AIS Receiver to Lowrance HDS-5 or HDS-7
Ridge Runner posted 04-25-2010 12:27 PM ET (US)   Profile for Ridge Runner   Send Email to Ridge Runner  
I'm a little confused about the wiring to interconect a Lowrance HDS-5 to a Standard Horizon Matrix AIS GX2100.

The manual for the GX2100 shows the connections as follows:
GREEN - NMEA Ground (-) - Connect to NMEA (-) Connections of GPS
BLUE - NMEA Input (+) - Connect to NMEA (+) Output of GPS
GRAY - NMEA Output (+) - Connect to NMEA (+) Input of GPS
BROWN - AIS Data Output (+) - Connect to NMEA 34.8K baud (+) input of GPS

The manual for the Lowrance HDS-5 shows the connections as follows:
HDS-5 YELLOW TX (+) to Device Recieve (+)
HDS-5 BLUE TX (-) to Device Recieve (-)
HDS-5 ORANGE RX (+) to Device (+)
HDS-5 GREEN RX (-) to Device Transmit (-)
HDS-5 Shield (ground) to Device Ground

Can someone tell me the correct hook-up?

jimh posted 04-25-2010 01:01 PM ET (US)     Profile for jimh  Send Email to jimh     
To interconnect NMEA-0183 devices, you connect an output to an input.

From GPS output to RADIO input, use:

GPS ------------->RADIO
Yellow (TX +) --->Blue (+ input)
Blue (TX -) ----->no connection; insulate and store
Shield ---------->Green (NMEA GND)

From the RADIO output to the CHARTPLOTTER input, use:

Gray (Tx +) ----->Orange (RX +)
Green (NMEA GND -->Green (RX -)


HDS-5------------> GX2100
Yellow ----------> Blue
Blue-------------> No connection
Orange -----------> Gray
Green ------------> Green
Shield -----------> Green

If the Chartplotter can show AIS data, you would use the radio's AIS data circuit (BROWN) in place of the GRAY.

SJUAE posted 04-25-2010 03:30 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
Yes I found this confusing as the GX2100 uses a common green cable.

My setup was worse as I had two HDS-5 to connect and run the AIS brown and green/shield to the second HDS as I thought you had to also have the gray connected. Only the HDS-8 and 10 have 2 inputs

I have not checked if it's all working yet as I don't have a MMSI number so DSC and AIS is not fuctioning on the GX2100 until the number is entered.

Don't forget to set your output to 4800 baud no parity for output and 34800 for input of AIS on your HDS


Ridge Runner posted 04-25-2010 04:00 PM ET (US)     Profile for Ridge Runner  Send Email to Ridge Runner     
Thank you, Jim.
Steve, I also have two HDS-5's but didn't think I could interconnect all three devices. I was going to leave one HDS-5 as the sonar unit and one as the chartplotter. Do you know if the HDS-5 can show AIS data?
jimh posted 04-25-2010 06:06 PM ET (US)     Profile for jimh  Send Email to jimh     
Ridge'--better hook it up and see if my plan works. I think it will, but it would be good to have confirmation.

Interconnecting serial data outputs and inputs can be tricky. Make sure the various ports are configured for the same parameters of baud rate, stop bits, and parity. Then make sure the software is configured to be sending the proper data on the output, as well as the receiver software configured to look for the proper data on the input. It can be a mess to get working because typically nothing happens unless everything is correct. That makes it hard to troubleshoot.

SJUAE posted 04-26-2010 06:51 AM ET (US)     Profile for SJUAE  Send Email to SJUAE     
Ridge Runner

The HDS can show AIS data, but I can't see it yet due to no MMSI number so it does not even show on the GX2100 screen.

I would of connected the AIS to your HDS using as a chart plotter and the other in and out to the other HDS.

I have both HDS interconnected as I have the Broardband sounder so at the moment both sonars (broadband and normal 83/200) can be shared on both HDS's

I read elsewhere that most new systems need/have 2 NMEA0183 inputs and 1 output and this was required to have both a VHF and AIS connected

Jim may well be correct but I never thought that the brown wire could dual function as the baud setting is 34800 for AIS and not 4800 for other VHF/DSC functions which the grey wire would use.


StandardHorizon posted 04-30-2010 07:29 PM ET (US)     Profile for StandardHorizon  Send Email to StandardHorizon     
Please contact me for connection details on the Matrix AIS.

Best regards,

Scott Iverson
Product Manager
Standard Horizon

Hoosier posted 04-30-2010 11:19 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
I had the same questions when I was hooking my SH Eclipse DSC to my HDS-5. The tech support from SH was outstanding, here's what the told me

"The connections will be as follows:

GX1100S blue (RX+) to HDS yellow (TX+)
GX1100S purple (TX+) to HDS orange (RX+)
GX1100S green (RX-/TX-) to HDS blue (TX-) and HDS green (RX-)

The GX1100S shield is for an external speaker and should not be
connected to the HDS shield."

I did what they told me and it worked.

jimh posted 04-30-2010 11:58 PM ET (US)     Profile for jimh  Send Email to jimh     
No fair using the "purple" wire. That was not included in the original posting.
jimh posted 05-01-2010 12:01 AM ET (US)     Profile for jimh  Send Email to jimh     
If the HDS has an active data-out-inverted (-), you should not connect it to the power common; it's better to let active inverted outputs float.
SJUAE posted 05-01-2010 02:59 AM ET (US)     Profile for SJUAE  Send Email to SJUAE     
I have 2 HDS-5 connected to each other via a broadband network unit

I wired them as:

Right GPS Unit:-
VHF AIS OUTPUT brown + to GPS Orange RX + (set to 38000) VHF ground green - to GPS Green RX - VHF input blue + to GPS Yellow TX + (set to 4800) VHF ground Green - to GPS Blue TX -

Left GPS Unit:-
VHF NMEA output Grey + to GPS to GPS Orange RX + (set to 4800) VHF ground green - to GPS Green RX -

Therefore the green is connected 3 times on the VHF, 2 from right GPS and 1 times from left GPS

Not used
Shield Ground

I havent checked if this configuration works as I dont have a MMSI number currently

So I emailed Scott at Standard Horizion last night and he advised a multiplexer would be required wired like this : multiplexer.jpg

I waiting for him to clarify a few other points. I will be dissapointed in I need a multiplexer. I presume the HDS-8/10 do not as they have 2 in and 1 out connections


Ridge Runner posted 05-01-2010 09:38 AM ET (US)     Profile for Ridge Runner  Send Email to Ridge Runner     
Jim - The GX2100 does not have a "purple" wire.

Steve - Standard Horizon has alos told me that I would need a multiplexer.

I was also told from Jim at BOE Marine - " You can enable the GX2100 with GPS data from the HDS unit. But the GX2100 will not transmit AIS data back to the HDS unit. You need a nmea2000 ais source to work with the HDS unit.
Currently, the only NMEA AIS is the Garmin VHF-300 ($700). Of course, you can buy the 600 series (send/receive AIS data) for about $1100."

jimh posted 05-01-2010 11:16 AM ET (US)     Profile for jimh  Send Email to jimh     
I'll reach out to Scott at Standard-Horizon so that we might have his opinion on the proper interface between the GX2100AIS and the HDS series presented in this discussion.
SJUAE posted 05-01-2010 03:03 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

The wiring diagram with multiplexer was from Jim at Standard Horizon he emailed it back to me in a matter of hours.


jimh posted 05-01-2010 03:19 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--I understand that information can be sent via private email. I am interested in information that can be shared in this discussion. I am not particularly interested in a solution that involves buying more equipment to establish the connection between a Standard Horizon GC2100AIS and a Lowrance HDS chart plotter. There should be a solution that permits direct connection. That is what I hope to explore further.
jimh posted 05-01-2010 03:26 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--In the diagram you show above (see link), there is no NEMA-0183 output from the multiplexer that is connected to the GX2100AIS. The GX2100AIS needs to have position data (usually from a GPS) supplied to it in order to be able to send a DSC message with its position. That interconnection diagram does not show such a connection.

There must be some additional wiring not shown in the diagram.

SJUAE posted 05-01-2010 04:19 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
Found the wiring links now at Standard Horizon

Main page all units: ProdCatID=83&encProdID=F858763BB81027701141A0167DE2A031

HDS-5/7 FileCatID=86&FileName=Wiring%20to%20Lowrance%20HDS5%20%26%207.pdf& FileContentType=application%2Fpdf

HDS-8/10 FileCatID=86&FileName=Wiring%20to%20Lowrance%20HDS8%20%26%2010.pdf& FileContentType=application%2Fpdf

If you have 2 HDS-5/7's I would of hoped that no multiplexer was required


jimh posted 05-01-2010 04:24 PM ET (US)     Profile for jimh  Send Email to jimh     

Readers please take note that among the LOWRANCE chart plotters in the HDS series there is a distinction in the data outputs which is very important to observe and take into consideration when making interconnections. The devices are divided into two categories: the HDS-5, HDS-7 form one category, and the HDS-8, HDS-10 form the second category.

HDS-5, HDS-7 Data Cable
In the Lowrance HDS-5 and HDS-7 devices, the data cable consists of five conductors. There is a single serial data I/O port which operates using RS-422, a balanced data output configuration. The functionality of the wiring is as follows:

HDS-5, HDS-7 COM-1 Data Port

YELLOW = Data TX (non-inverting) (+)
BLUE = Data TX (inverting) (-)
ORANGE = Data RX (non-inverting) (+)
GREEN = Data Rx (inverting) (-)
SHIELD = Shield Ground

(I use the term "non-inverting" in lieu of the "+" notation, and the term "inverting" in lieu of the "-" notation, because there is really not a polarity involved as most might think.)

The Data TX (inverting) (-) circuit (BLUE wire) should not be tied to ground. If connecting to a single-ended serial data input device, leave the BLUE wire floating, or tie to ground via 100-ohm resistor.

HDS-8, HDS-10 Data Cable
In the Lowrance HS-8 and HDS-10 devices, the data cable appears the same as in the others, but there is a significant difference. The configuration of the device can be controlled in software. The serial data I/O can be set up as either ONE RS-422 port or as TWO RS-232 ports.

When configured as a single RS-422 port, the data cable wiring is the same as shown above. Then configured as two RS-232 ports, the data cable wiring is as shown below:

HDS-8, HDS-10 COM-1 and COM-2 Data Ports

YELLOW = Data Tx COM-1
ORANGE = Data Rx COM-1

BLUE = Data TX COM-2
GREEN = Data Rx COM-2


jimh posted 05-01-2010 04:40 PM ET (US)     Profile for jimh  Send Email to jimh     
The above is my interpretation of the Lowrance devices after a careful reading of their documentation. I have not verified any of this in actual practice, as I don't have an HDS unit from each category to experiment with.

Assuming my interpretation is correct, the implication is that connecting an external AIS receiver to an HDS-8 or HDS-10 device should be possible without a multiplexer. One serial data port on the HDS-8 or HDS-10 could be set for the standard 4800-bps configuration, and a second data port set for the 34,800-bps need to get the AIS data from an external receiver (such as the Standard-Horizon GX2100AIS).

SJUAE posted 05-01-2010 04:50 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
Sorry on the Standard Horizon main page link above you need to go to the files tab to see the wiring for other GPS/Plotters

Apparantly you can't stack multiple 0183 outputs on the same input port regardless of speed

I'm hoping if I set 1 HDS unit to com port 1 4800 and the other HDS unit to com port 2 38400 it may work

Jim sorry about private mail but I thought it was an easier way to get a reply from Scott and post it here, I did not check the diagram.

Jim I'm guessing but as the HDS-5/7 has a Com 1 or 2 setting according to the manual its slighly different to the HDS-8/10 use you note


SJUAE posted 05-01-2010 04:57 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

My link above to Standard Horizon GX-2100 wiring for the HDS-8/10 confirms your findings that no multiplexer is required.

It seems a multiplexer is required for a single HDS-5/7 but I'm not convinced for a dual HDS-5/7 setup to a GX-2100.


jimh posted 05-01-2010 09:44 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--Thanks for the link to the Standard-Horizon wiring diagrams. I was pouring over the manuals for the Lowrance devices this afternoon, and I did not see all of that documentation on the Standard Horizon website.

As for using the HDS-5 and HDS-7 with an external AIS receiver, I don't think it is a huge disappointment that this cannot be easily done. The smaller displays are already filled with information, so adding an AIS overlay or an AIS separate page is probably too much for them.

As Steve pointed out (some time ago in another discussion) you can often buy two of the smaller devices for less than one of the larger displays, and the total screen real estate might be larger.

SJUAE posted 05-02-2010 03:20 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Your right the single HDS-5 or 7 screen can soon fill up with data, especially if you have structure scan fitted and have a 3 way split screen (eg sonar, structurescan and downscan)

This is when the dual screens really help and you can configure them both for optimal viewing depending on your current focus of activity.

I'm still hopeful for getting AIS to work on the dual HDS-5's without a multiplexer as I'm guessing they will work not unlike a HDS-8/10 when networked via the structurescan unit.


SJUAE posted 05-04-2010 04:03 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Revised wiring diagram for twin HDS-5/7 to SH GX2100 using a multiplexer from Scott at Standard Horizion updatedmultiplexer.jpg


SJUAE posted 05-22-2010 03:35 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
I finally got around to part testing my HDS-5's and my GX2100

I got the GX2100 to receive input from the Lowrance so the AIS display works on the GX2100. The Speed Over Ground (SOG) always read 2- to 4-MPH less than my two HDS units, which is strange as it originates from the HDS to the GX2100.

I could not get the AIS to display on the HDS so I may (if I can be bothered) have to get a multiplexer although I did not have a MMSI number, which may stop it working.

Still can't check DSC as I don't have a MMSI number


jimh posted 05-23-2010 09:54 AM ET (US)     Profile for jimh  Send Email to jimh     
Steve--If I understand correctly, your situation is as follows:

GPS to Radio
The GPS receiver in the Lowrance HDS-5 is sending position data to the Standard-Horizon GX2100AIS radio

Radio AIS to Multi-function Display
The Standard-Horizon radio is not communicating with the Lowrance HDS-5 to send AIS data for display

Have you tested with another boat with a DSC radio to see if you can display the position of another boat on your chart plotter when you receive a remote position DSC transmission?

SJUAE posted 05-23-2010 03:05 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Your summation is correct

I cannot currently try DSC functions as these are disabled on the GX2100 until I enter a MMSI number.

(FYI export models from the US do not have to ship with a MMSI number)

I need to get a MMSI number here but it's not as simple or cheap as the US/UK and elsewhere.

I also note the HDS has the ability to add a MMSI number but I assume it's not a onetime operation that can only be changed by return to the factory like the GX2100.

I'm a little disappointed with the HDS-5 as the manual for both the HDS-5/7 show the RS232 ports being able to be set to com 1 or 2 which is only possible on the HDS-8/10

I had hoped I could get one unit to send GPS data and receive DSC data and the other HDS to receive AIS data

Just checked Lowrance site no wonder it's slow new software release HDS 3.0 (280 MB file) and now supports Mercury Smartcraft interface

Provides real time monitoring of Mercury Engine Data on HDS displays.

engine RPM, engine voltage, oil & water pressures, fuel flow, and more

•Eliminates the need for the consumer/boat builder to install dedicated gauges to view this information
•View more information, faster than using standard gauges

Other Considerations/Equipment
•Requires separate purchase of SmartCraft Merc Monitor from Mercury

•Standard NMEA 2000 network setup and activation
•Some configuration may be required;auto-configuration option is available.
•More hands-on required for multiple engine set-ups.
•Info Screen to Display HDS_3_0_RELEASE_NOTES.pdf

The update also addresses some of the potential clutter issues more prone on the smaller screens showing AIS data, so maybe I should get a multiplexer now

I certainly will have to refigure my advice on twin HDS-5/7 over single other larger units if AIS is required as you need to factor for the $200 multiplexer.


jimh posted 05-23-2010 05:13 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--I suspect the Mercury integration is no big deal in this Lowrance software update. I assume purchase of the Mercury proprietary gateway does most of the heavy lifting. Once the Mercury engine data gets into NMEA-2000 PGN format, any display should be able to show it.
jimh posted 05-23-2010 05:17 PM ET (US)     Profile for jimh  Send Email to jimh     
A DSC radio that does not have an MMSI number configured is probably not going to cooperate much with DSC operation. I know your situation in the United Arab Emirates makes getting an official MMSI number somewhat difficult.

I wonder if you could use an MMSI from BoatUS to jump-start the radio into DSC operation. I don't know what the legality of that would be in the UAE. Proceed with caution.

bluewaterpirate posted 05-23-2010 05:20 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Steve .....

Are your two Lowrances connected via an NMEA 2000 Network (N2K) network? If so you should be able to send all the AIS data from your HDS unit that is connected to the GX2100 via NMEA 0183 connectivty to your other HDS unit via the N2K newtork.

The HDS unit connected to the GX2100 has to be set up to do network bridging ... on Garmin and Raymarine MFD's the settings are OFF/ON/AUTO. Auto is the setting you want to use if your two MFD's are connected via N2K.

The beauty of this is you don't need mulitplexor. The other key is DSC and AIS data coming from the GX2100 comes on different ports so they communicate with your MFD independently of one another.

I haven't installed any Lowrance equipment in over a year so I'm not sure if the HSD units have the newtork bridging feature.

What it does is the unit connected to the GX2100 receives the DSC/AIS date via NMEA 0183 then it coverts the NMEA 0183 data into N2K format and shares with the other MFD's on the N2K newtork.

Hope this helps out.


SJUAE posted 05-24-2010 03:40 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Re Smartcraft:
Agreed the Mercury black box does the hard work, but at least we know Lowrance has tested it and adjusted their software to suit.

Apart for some legal issues I would of tried the BoatUS MMSI number just as a test case but the MMSI number cannot be reversed on the GX2100 without sending it back to the US. So I will have to wait and get an offical number here which is a pain as I am treated the same as a full commercial vessel and so over 400USD a year.


Good point on the N2K bridging I'm not sure if I have it right this doc seemed to explain what’s shared across the different networks

HDS System Overview

It was not until I looked at this last week I realised that the N2K was not shared over the lowrance network so I have asked my yard to add a second drop cable and Tee so both units are on the N2K.

I can then test if it works as you suggest. You would of thought that given that the Lowrance HDS-8/10 and higher end Garmin and Raymarine can handle two NMEA 0183 inputs so should my twin HDS-5's without a multiplexer.

Still all this does not explain why my GX2100 SOG is 2-4 mph less that the 2 HDS-5's display


jimh posted 05-25-2010 11:52 PM ET (US)     Profile for jimh  Send Email to jimh     
[Fixed bad link above.]
jimh posted 05-26-2010 10:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--Thanks for pointing to that interesting document from Lowrance which explains how two Lowrance devices can share information among them via either their NMEA network connection or their Lowrance Ethernet connections.
jimh posted 05-27-2010 08:18 AM ET (US)     Profile for jimh  Send Email to jimh     
I have had some correspondence with Standard-Horizon and Brookhouse on the use of a NMEA multiplexer to interconnect the Standard-Horizon GX2100AIS VHF Marine Band radio and AIS receiver to a Lowrance HDS-5 or Lowrance HDS-7 chart plotter. Brookhouse recommends using their multiplexer model:

Brookhouse Multiplexer AIS, Product code NMUX-AIS

and indicates the recommended wiring in this diagram: gx2100_hds57.pdf

When ordering the Multiplexer AIS include a note indicating it is for use with the GX2100AIS and the HDS-5 or HDS-7, and Brookhouse will provide a special label on the multiplexer that will show the necessary wiring. They refer to this special model as the Multiplexer AIS MATRIX.

The diagram linked above is much clearer than the previous diagram, as it shows direction arrows to indicate the flow of data on the signal lines, and it also removes all ambiguity about where connections are located on the multiplexer device.

The multiplexer solves the fundamental problem of the HDS-5 and HDS-7 having only one serial data port to receive information. Because the radio has two serial port outputs that will be sending information, to combine these and send them to the chart plotter requires a multiplexer. The multiplexer will also handle the difference in baud rate used on the two serial ports of the radio.

For more information on the Brookhouse Mutiplexer AIS model, see their excellent website:

The cost of the multiplexer is about $200, and cost of shipping from New Zealand will be about $12.

jimh posted 05-27-2010 08:30 AM ET (US)     Profile for jimh  Send Email to jimh     
If planning on using your chart plotter with an AIS receiver such as the Standard-Horizon GX2100AIS, it might be reasonable to look into the serial port arrangement to be certain the chart plotter had two serial ports available, and the serial ports could be set to different baud rates. This would eliminate the need for the multiplexer, saving about $220. In the case of the Lowrance product line, one has to move up to the HDS-8 model to get two serial ports. The cost to move to the HDS-8 from the HDS-7 model is roughly a $700 increase in price, but from this you could deduct the roughly $220 cost of the multiplexer.
jimh posted 05-27-2010 08:41 AM ET (US)     Profile for jimh  Send Email to jimh     
In regard to the serial data output from the Lowrance HDS-5 or Lowrance HDS-7, the configuration appears to be a differential signal with the data output carried on the wiring as follows

HDS-5/7 BLUE TX (-)

As a general rule, with active differential data ouput, the inverting output is usually marked with a minus sign (-), but this is really not a polarity mark. If the differential output feeds a single-ended input, the inverting output is typically not needed, and it it often left floating. In some configurations, connecting the inverted data output directly to ground can be a problem. However, both Standard-Horizon and Brookhouse indicate that the inverting data output (the BLUE wire) from the HDS-5 or HDS-7 needs to connect to the signal common or ground of the unbalanced input of the multiplexer.

SJUAE posted 05-27-2010 08:58 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Thanks for the info

I managed to get an additional drop cable so now both of my HDS-5 units are linked by MNEA 2000 and Lowrance network using the broadband LSS-1 unit.

If Tom is correct the Lowrance units can bridge any NMEA 0183 inputs to NMEA2000 so I may be lucky and get some AIS data to the HDS's

I will try this weekend but I think now finding that the HDS-5 cannot set the RX/TX independently to different bauds (unlike the HDS-8/10) I may need to change the wiring so that one unit is dedicated to TX GPS data to the GX2100 and RX DSC data from the GX2100 as both of these are at 4800

The other unit can be set to RX AIS data from the GX2100 at 38400 and bridged to NMEA 2000

I'm shooting in the dark here as unlike Jim I don't really understand how a common green is used 3 times on the GX2100.

It’s worth a try IMO even if I'm completely misguided by my simple understanding of electronics, before spending $200 on a multiplexer


jimh posted 05-27-2010 09:01 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve's situation with the Lowrance HDS-5 and HDS-7 integration with a Standard-Horizon GX2100AIS radio is somewhat unique: he has two Lowrance units. It may be possible to connect the radio serial data to both units, setting one Lowrance to get the 4800-bps data and the other to get the 38,400-bps data; the two units may be able to share this data via their network connections using either the NMEA-2000 network or the Lowrance Ethernet network. I am hoping Steve can try this and fill us in on the results.
SJUAE posted 05-29-2010 02:10 AM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Will do, no chance yesterday with a birthday party onboard and beach BBQ.


jimh posted 05-30-2010 10:55 AM ET (US)     Profile for jimh  Send Email to jimh     
The fundamental problem being discussed here is a common problem in interconnecting an AIS receiver to other devices. The standard data rate for the output from an AIS receiver is 38400-bps. (ASIDE--I am searching for a good reference for this from an official standard. If you know of one, please pass it to me via email.) To connect the information from the AIS receiver to a display device, the display device--typically a GPS receiver and chart plotter combination--must have its serial port set for 38400-bps. On most GPS-chart plotter devices, it is not difficult to change the serial port speed to 38400-bps. But now comes the problem.

The GPS-chart plotter device will need to send GPS information to the VHF Marine band radio. The typical radio serial port will be operating at 4800-bps. If the GPS-chart plotter device only has one serial port, and if the serial port is set to 38400-bps, then that serial port cannot be used to connect to the radio. The solution to the problem of a GPS-chart plotter with only one serial port lies in three options:

--buy a new chart plotter that has two serial ports; set one for the 38400-bps rate and the other for the 4800-bps rate. Buying a new chart plotter is the most expensive. As we saw in the above discussion, upgrading from a HDS-7 to an HDS-8 to get the second serial port costs $700.

--buy a NMEA-0183 multiplexer to combine the two data streams going to the GPS-chart plotter device into one. Buying a NMEA multiplexer costs about $220. The multiplexer may also be handy to have to solve other problems in connection in the future, as you will not be using all of its serial port inputs. You'll have some room to grow, if needed.

--buy a separate GPS receiver to send GPS information to the radio at 4800-bps. Buying a separate GPS receiver is not very expensive, and is probably the least expensive option in this case. You can get a modern, very high-performance GPS receiver with serial data output for about $50 to $70, depending on the mounting. (See links below for sources of a suitable GPS receiver.)

USGLOBALSAT make an inexpensive but very good GPS receiver with NMEA-0183 serial data output which could be used as a second GPS receiver to feed position information to the radio. The GPS receiver is available in two mounting styles. To operate the receiver you must supply power at only 3 to 5-Volts DC, so some sort of power regulator chip must be added to the typical vessel 12-volt distribution. A power regulator chip to turn 12-volts into 5-volts costs only a few dollars, and it should be easy to fabricate. The USGLOBALSAT factory documentation mentions a special cord set to obtain the power and to provide a DB9 plug from the attached PS-2 style connector. I believe that you could simply cut off the PS-2 style connector and use the wires in the cable to attach directly to the radio serial port and your 5-volt DC power source. However, I have not tried this myself. I would be interested to hear from anyone who does try it.

The model 355 is only MSRP at $50 and may be bought for less at on-line sellers;

--or a more expensive model 350P (MSRP $67) with a plastic mushroom enclosure that would be suitable for mounting on the deck of a boat:

I have not tried either of these serial output GPS receivers, but I have purchased the USGLOBALSAT GPS receiver with USB output, the model 353:

The performance of this GPS receiver is exceptionally good, and I bought it for only $35 from an on-line reseller.

jimh posted 05-30-2010 12:34 PM ET (US)     Profile for jimh  Send Email to jimh     
To provide a low-current 5-volt supply for the USGLOBALSAT GPS receiver, an inexpensive voltage regulator chip from the 7805-series could be used. You can find them at RadioShack for under $2.
jimh posted 05-31-2010 09:01 AM ET (US)     Profile for jimh  Send Email to jimh     
Upon some further thought, I must revise my analysis given above in regard to using a second GPS receiver as a solution to the problem of interconnecting the VHF Marine Band radio with integral AIS receiver to a chart plotter. The second GPS receiver approach will not provide a total solution. There is more to the problem.

In integrating the VHF Marine Band radio to the chart plotter, we would also like to take advantage of digital selective calling (DSC) features. One desirable feature of interconnection of the radio and plotter is the ability to display on the chart plotter the position of another vessel which has been obtained as a result of DSC remote position poll request. This requires the radio and chart plotter to be connected in some manner via NMEA communication so that the radio can cause the chart plotter to display a remote position of another vessel obtained via DSC.

There is also the potential for further integration of the chart plotter and radio. It may be possible in some cases to have the chart plotter act as a control device for the radio. That is, the operator may be able to perform an input action to the chart plotter, such as pushing an on-screen button on a touch screen display, which will cause the radio to perform some further action, such as changing channels or making a further DSC call to another vessel. This sort of integration may be limited to cases where the radio and chart plotter are made by the same vendor.

SJUAE posted 05-31-2010 04:54 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

Hopefully the wiring is reconfigured now, Got the yard to do it as it was a touch hot the last few days at 120F.

I have seen a few screen shots of what AIS is suppose to look like on the HDS and the information page for a selected target but I have not seen one for a DSC polled vessel so I'm not sure what to expect.


jimh posted 05-31-2010 07:42 PM ET (US)     Profile for jimh  Send Email to jimh     
To get a remote position from another vessel via a DSC remote position request will require having an MMSI set up in the radio. I think Steve is temporarily unable to get an MMSI in his radio due to a bit of bureaucratic high cost.

I owned a DSC radio for about two years before I found another vessel that also had a DSC radio and could give me a reply to my request for a remote position poll. I got so frustrated trying to find another DSC vessel I was about to buy a second DSC radio just so I could see if my first radio was working properly.

Several of the people I regularly boat with had DSC radios, but they typically had radios which were only compliant with the very early specification of SC-101 DSC capability. Their radios could only send an emergency broadcast with their position, and could not respond to other DSC radio requests for position information. I believe you need two Class-D rated DSC radios to exchange remote position data in an non-emergency situation.

jimh posted 06-01-2010 07:51 AM ET (US)     Profile for jimh  Send Email to jimh     
The purpose of the automatic identification system (AIS) is to help ships avoid collisions at sea. AIS can help in collision avoidance in two important ways. Primarily, it acts like a RADAR so that ships can easily see each other on their AIS displays. A vessel equipped with AIS will see the position of other AIS vessels relative to her own position, and--also very important--learn the identity of the other vessel, including the other vessel's name and her MMSI. This allows radio communication to be established without any ambiguity.

As an example, consider two vessels approaching each other on a collision course. Without AIS, one vessel might try to hail the other via radio, but they would not know the other vessel's name or callsign. They could only make a generic radio call. There have been cases of mistaken identity which have occurred in crowded sea lanes, where two vessels on a collision course thought they were in radio communication, but actually there was a third vessel that was mistakenly participating.

DSC radios can make specific calls to another DSC radio, but you first have to know the MMSI of the other radio. With AIS, you learn the MMSI of the other vessel! With a well designed AIS and DSC radio, it should also be easy to initiate a DSC call to another vessel by using the MMSI data from the AIS receiver. The radio should be able to pass the MMSI information from the AIS receiver to the DSC radio without the operator having to manually enter the MMSI data into the DSC radio.

On most of the less expensive DSC radios, entry of another vessel's MMSI is quite a tedious process because typically these low-priced radios do not have a numeric keypad for data entry. The MMSI has to entered using a cumbrous method of rotating a dial to select a digit, then pushing a button to enter the digit. This is a time-consuming and error-prone process. With good integration between an AIS receiver and a DSC radio, manual entry of an MMSI to call an AIS target ship will not be necessary.

bluewaterpirate posted 06-01-2010 09:13 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I went off shore yesterday on a friends boat. I installed a GX2100 on it last week. We had three mechant ships pass within three miles of us. We had solid AIS from one vessel on the his Garmin 5212 and GX2100. We received no AIS data from the other two.


SJUAE posted 06-01-2010 04:56 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

I think AIS is only transmitted every 3 minutes while at anchor.

Maybe based on your range setting and speed made you miss them.


bluewaterpirate posted 06-01-2010 08:22 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
All our equipment was setup correctly ... activation range and display range were set to 15 miles and CPA alarm 3 miles.

We were 70 miles offshore in the gulf stream. Three of the merchants were tracking to to the SSW between 17 - 21 knots and one to the NE at 17 knots. We picked up the one with AIS data at 14 miles on the SH gx2100 and on radar at 11 miles. His course was 200 at 18 knots. They all passed within 1 - 3 miles of us. We were unable to raise them on three different radios. I think they had their AIS equipment in standby which wouldn't surprise me at all.

Just have to wait for my next offshore excusion.

The SH gx2100 worked great had good vhf communications all day with other fisherman in our area.


SJUAE posted 06-02-2010 03:16 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

70 miles offshore I would almost be in Iranian waters :)

If they had it on standby it almost defeats the objective of AIS :(

Was your SOG the same on the Garmin and the GX2100 ?


bluewaterpirate posted 06-02-2010 04:31 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Yes all the info from the Garmin was displayed correctly on the SH.

Side note ....

I spent alot of time in the Persian Gulf as an adivsor to the Iranian/Saudi navies. I was stationed in Bandar Abbas Iran starting in late 1978. Was there for 10 months.... got out just ahead of the fall of the Shah. After that I spent three years in Suadi Arabia ... then six deployments to the gulf on Navy ships escorting tankers and as a participant in the first Gulf War. Spent the better part of my adult life in the region.

Interesting area of the world for sure .. rich in history.


SJUAE posted 06-11-2010 04:19 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     

It may be possible to connect the radio serial data to both units, setting one Lowrance to get the 4800-bps data and the other to get the 38,400-bps data; the two units may be able to share this data via their network connections using either the NMEA-2000 network or the Lowrance Ethernet network. I am hoping Steve can try this and fill us in on the results

No joy I’m afraid, seems like a multiplexer is required.

I set the serial ports to the required settings and went in to the network send and receive sentences and switched them all on and the NMEA2000 both send and receive to on for both units.

I know the Lowrance Ethernet is working as the transom skimmer sonar is only connected to the left HDS and is transmitted to the right one via the structure scan Lowrance Ethernet unit.

The GX2100 is getting the GPS signal from the HDS as the AIS and other nav data is shown on the screen

My guess is the different sentences sent back and forth to the GX2100 using the common green wire are not synchronised or something from the 2 HDS units.

I did notice that the HDS-8/10 when using both ports are RS232 not RS-422 on the HDS-5/7

I did have some good news the reason my SOG was different on the GX2100 to my HDS's was due to it being in knots not mph, a quick slap round the back of my head fixed that :)


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