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Author Topic:   GPS, Fishfinder, and VHF
junniebugg posted 03-20-2006 12:02 PM ET (US)   Profile for junniebugg   Send Email to junniebugg  
I have a Garmin 76 GPS and Hummingbird Matrix 17 depth finder. Based on
what I read in the West Marine catalog, they can be linked with the
purchase of a GPS connection cable. I need to purchase a VHF marine
radio. Based other material that I read in the West Marine catalog you
can link a GPS to a VHF, which can send out a DSC distress signal with
the boats coordinate position.
My question is; can all 3 be connected by one cable to each other?
Cabela's Marine catalog has a GPS Connection Cable, which is referred
to as a Y cable. Would that be a 3-way cable that would link all three?

In reviewing my Matrix 17 Operations Manual, I was only able to locate limited information regarding attaching the GPS to the Matrix. I called the
Hummingbird Customer Resource Center for help. The experience was
awful. I spoke with a woman who knew nothing about a Matrix and could
not speak in complete sentences. She disconnected me because she could
not answer my questions.

Can anyone out in the Whaler World enlighten me?

Chuck Tribolet posted 03-20-2006 02:20 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
You can run one NMEA output to multiple (up to about four)
NMEA inputs, but each input can only be connected to to one

The fishfinder has only NMEA out.
The GPS has NMEA in and out.
The radio will have NMEA in, and some have NMEA out.

So who can do what with the other guy'd data?

The GPS can record depth with waypoints and maybe in the track

The radio can take position data from the GPS. The radio may
(if more expensive) be able to send position data to the GPS
which may (if more expensive) be able to display it.

But I don't think your GPS 76 can display it. So here's what
I'd do:

Fishfinder NMEA out (can't find the color code) to GPS NMEA in
(white). You'll need to buy the Humminbird GPS connection

GPS NMEA out (brown) to radio NMEA in (don't know color because
don't know the radio).

All three grounds together. Keep the ground and signal
cables short and together (fishfinder ground and NMEA out together, etc).


Chuck Tribolet posted 03-20-2006 02:22 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
As an explanation of my first paragraph:

If you have three people standaround talking, if one talks,
two can listen, but if two talk at the same time, the third
will have trouble understanding.


jimh posted 03-20-2006 05:56 PM ET (US)     Profile for jimh  Send Email to jimh     
What sort of NMEA-0183 protocol data does the SONAR provide to the Chartplotter/GPS?

What sort of NMEA-0183 protocol data does the Chartplotter/GPS provide to the SONAR?

Chuck Tribolet posted 03-20-2006 07:28 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The fishfinder provides what it knows to the GPS: depth, speed,
water temp etc. What the GPS can exploit is another question.

The GPS can't provide anything to the fishfinder because the
fishfinder doesn't have NMEA IN.


jimh posted 03-20-2006 10:16 PM ET (US)     Profile for jimh  Send Email to jimh     
As best as I can make out, the problem at hand is this:

The SONAR, a Humminbird Matrix 17, can accept input from a GPS in order to allow the SONAR to display some of the data on its large screen. This is a very simple connection:

GPS NMEA-output to SONAR MNEA-input.

Also, it is desired to interconnect the GPS to the VHF RADIO. The radio can accept inputs from a NMEA source. This is also a simple connection:

GPS NMEA-output to RADIO NMEA-input.

Solution: Investigate the GPS to see if it has multiple outputs. If yes, configure the outputs to send the proper NEMA data sentences to the device connected to each output. If the GPS has only a single output, connect it to both the SONAR input and the RADIO input. Configure all the necessary sentences to be sent on the single output.

The owner's manuals of all the devices will provide the details about what pins on what connector to use. The GPS will have to be configured to transmit the proper data sentences.

Chuck Tribolet posted 03-21-2006 12:51 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Jim: FOR THE THIRD TIME: The sonar has no NMEA IN. It can't
accept data from ANYTHING. It does have NMEA OUT that can
be used to send depth, speed over water, water temp, etc.
to some interested instrument.

But if it did, you wouldn't need multiple outputs. You can
tie one NMEA output to multiple inputs. The max fanout,
IIRC (and this is real fuzzy) is four.


junniebugg posted 03-21-2006 04:52 PM ET (US)     Profile for junniebugg  Send Email to junniebugg     
Chuck & Jim

The following is from the West Marine web page Product Advise / West Advisor:

The latest on Digital Calling Service (DSC)


Digital Selective Calling (DSC) is a technology that allows a VHF radio to send digitally encoded information, including the vessel's ID number (MMSI or Maritime Mobile Service Identity), and its lat-long (if connected to a GPS). This is of the greatest (potential) use to recreational boaters if they are in distress, since a DSC radio can transmit an emergency message containing those key message elements to other vessels and shore stations, alerting them to your trouble. As soon as the distress message is sent, both the sending and receiving radios automatically turn to Channel 16 so that voice communications can follow.
The problem is that there is no nationwide network of stations monitoring Channel 70 for emergency DSC messages as present, so the Coast Guard is not likely to hear your Mayday call until around 2006. While there is discussion of interim solutions involving private companies, you cannot (yet) rely on the Coast Guard hearing your DSC distress transmission. However, commercial vessels over 300 tons are now required to monitor channel 70, and other vessels with DSC radios may very likely hear your distress call, and may be in a position to lend assistance. Plus, you are really no worse off using the DSC distress function, since it only takes a second or two, and returns your radio to Channel 16 where you can make a traditional Mayday transmission.

Before you can use DSC you must obtain a Maritime Mobile Service Identity (MMSI) number. When you apply for your MMSI you will submit information about you and your boat, which is then stored in the US Coast Guard's national distress database to be used in the event of a rescue situation. Until recently the only way to get a MMSI number was to apply for a ship radio station license from the FCC at a cost of about $90. Recently, the FCC has entered into agreements with MariTEL and BoatUS to issue MMSIs to "exempt " recreational vessels. Exempt vessels are classified as under 20 meters (65 ft.), not carrying a single side band radio or satellite communications equipment, and not using a VHF radiotelephone in foreign waters. To get free MMSI registration call MariTEL at 888-627-4835 (888-MARITEL).

Chuck Tribolet posted 03-21-2006 07:00 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Junie, there's no surprises there for either jimh or myself.

Boat US is one of several organizations handing out MMSIs.
They started at 338000000 in December 2000. A buddy has one
that's 338036757. Mine is 338000069, which was issued about
the first day Boat US was giving them out. (Before that you
had to pay the FCC about $100 to get one).

That said: The Humminbird Matrix 17 Manual only speaks of
NMEA output, however I found some specs on the GPS cable it
uses, and some more detailed reading of the Matrix 17 manual,
indicates that that it does indeed have both NMEA input and
output and can do stuff like display speed, time, and
distance. It doesn't appear to be able to display position,
though it mumbles about being able to store waypoints.

It also says it outputs the GGA NMEA sentence, which comes
from the GPS. So you COULD wire the VHF to the output of
the fishfinder, but I'd wire the GPS output to both the
fishfinder and the VHF. That way the fishfinder doesn't
have to be on for the VHF to know where you are.


bsmotril posted 03-22-2006 08:52 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
I have connected to NNEA receiving devices to a GPS with no problem. I used a 4 position terminal block and crimped ring connectors on to the wires within the cable, and then attached those to the terminal block. The data-out on the Gps goes to the Data-In on the two other devices. Data-In on the GPS goes to Data-Out on the two other devices. Grounds tie together. The electronics used to drive the signal levels will typically handle two devices without a problem. When you start getting more than that, you need some kind of splitter, hub, or repeater.
bsmotril posted 03-22-2006 08:53 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Phat Phingers this morning. The first sentence above should read "I have connected TWO NMEA devices together without problem".


sree954 posted 04-07-2006 06:24 AM ET (US)     Profile for sree954  Send Email to sree954     
dear sir,
i have icom FP 561 sounder cum GPS. i want to connect this unit to PC and wants to transfer lat/long position with deapth of that particular point to Computer is it can be possible


yours truly

ravi kumar

eportfolio posted 09-15-2007 09:44 AM ET (US)     Profile for eportfolio  Send Email to eportfolio     
Can the Garmin eTrex Legend GPS be connected to VHF radios with DSC capability?
jimh posted 09-15-2007 11:33 AM ET (US)     Profile for jimh  Send Email to jimh     
All VHF Marine Band radios use NMEA-0183 serial data inputs (except for the newly announced Lowrance radio which is the first to use NMEA-2000 connections), so any GPS device which can output NMEA-0183 data can be connected to any VHF Marine Band radio which accepts NMEA-0183 data.

To discover if a particular GPS device provides NMEA-0183 serial data input or output I recommend you consult the manufacturer's literature. For GARMIN devices I believe they have a rather elaborate website which provides data about their products, and this ought to be able to give you information on a particular device's NEMA-0183 capabilities.

davej14 posted 09-16-2007 11:10 AM ET (US)     Profile for davej14  Send Email to davej14     
It is also important to check capabilities of the NMEA-0183 "sentence" structures for each device. Connecting them does not insure that the data is usable.

To use expand upon Chuck's talking analogy, if one device is speaking in French but the other can only understand English then there will be no usable communication even though they can hear each other.

newt posted 09-17-2007 01:18 PM ET (US)     Profile for newt  Send Email to newt     
bsmotril, If I interpret your posts correctly, you have connected two devices to your gps, so you have a total of three devices linked together?

I currently have a Garmin gps (76 hand held) linked to a Garmin fish finder. The two talk nicely to each other. I can configure the fish finder to display data from the gps such as speed, time, bearing, ETA, etc, and I can also send way points, depth, and temperature to the gps. If I am understanding correctly, I could also simultaneously connect a DSC radio to the gps?

By the way, for Garmin GPS users, you can get connector plugs from . I bought (made a pledge) a couple male plugs from this guy and made my own interface cables.

Chuck Tribolet posted 09-17-2007 03:19 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Newt, you can have the GPS send position to the radio,
(two listeners (radio and fishfinder) on one talker (GPS)
is OK.


newt posted 09-17-2007 04:28 PM ET (US)     Profile for newt  Send Email to newt     
Thanks Chuck. I guess there is no reason for the radio and fish finder to talk to each other...or is there?
where2 posted 09-19-2007 08:14 PM ET (US)     Profile for where2  Send Email to where2     
The guys have been offering Do-It-Yourself Garmin plugs for pledges since I bought my Garmin 45XL (back when they were brand new '94-'96). They're an excelent resource for the Garmin plugs.

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