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Cobra MR F77W GPS to Garmin 740 NMEA 0183

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Cobra MR F77W GPS to Garmin 740 NMEA 0183

Old 06-04-2016, 03:13 PM
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Default Cobra MR F77W GPS to Garmin 740 NMEA 0183

I am trying to connect the two pieces of equipment together. A Cobra MR F77W GPS VHF radio to Garmin 740 I want to show positions of other boats on my chart plotter.

I have hoked them up as shown and tried NMEA standard and NMEA high speed on my 740, but I don't get any data on the diagnostics screen of my 740. I also have switched the VHF to external GPS and then it does not show any coordinates on the VHF display.
Any ideas? This is my first time working with a 0183 network.

cobra VHF ........................... garmin 740
white (+ NMEA data out ) -------- brown NMEA 0183 port 1 Rx (in)
brown (- NMEA data out ) --------- no connection
yellow NMEA 0183 +data in ------ blue NMEA 0183 port 1 Tx (out)
green NMEA 0183 -data in --------- ground
shield wire ------------------------------ ground
Old 06-04-2016, 05:50 PM
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I don't see where you got the data about the NMEA-0183 interface in the COBRA radio. I downloaded the manual from

https://www.cobra.com/sites/default/...S_MANL_ENG.pdf

and I cannot find the words "white" or "brown" in the literature. Please give a pointer to some literature from COBRA that corroborates your data about NMEA-0183 conductors.

I don't see where that radio has a NMEA-0183 output. It need that feature. It needs to send the sentences DSC and DSE to the radio. I don't find any mention of "DSE" in the literature.

Last edited by jhebert; 06-04-2016 at 06:15 PM. Reason: I substantially revised my reply once I discovered the radio owners manual lacked confirmation of the signals available.
Old 06-04-2016, 06:46 PM
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Originally Posted by jhebert View Post
I don't see where you got the data about the NMEA-0183 interface in the COBRA radio. I downloaded the manual from

https://www.cobra.com/sites/default/...S_MANL_ENG.pdf

and I cannot find the words "white" or "brown" in the literature. Please give a pointer to some literature from COBRA that corroborates your data about NMEA-0183 conductors.

I don't see where that radio has a NMEA-0183 output. It need that feature. It needs to send the sentences DSC and DSE to the radio. I don't find any mention of "DSE" in the literature.
You are correct. I also poured over the manual looking for the NMEA output. But, on my radio there is a pigtail with this tag. I think that is what I need!
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Old 06-04-2016, 06:58 PM
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Also, on page 2 of the manual, there is mention of the GPS output wires. I don't know why there is no other mention of it in the text.
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Old 06-04-2016, 09:53 PM
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Originally Posted by lightpants View Post
You are correct. I also poured over the manual looking for the NMEA output. But, on my radio there is a pigtail with this tag. I think that is what I need!
Going on what is shown in your illustration, it looks like the radio NMEA-0183 interface is as follows

TALKER A = White
TALKER B = Brown
LISTENER A = Yellow
LISTENER B = Green

Curiously, those are the recommended color coding for NMEA-0183. For the Garmin 700 series, see the signals listed at

http://continuouswave.com/forum/view...=9&t=816#p5307

There are two ports; neither is using the standard signals or colors:

Port 1
TALKER A = Blue
TALKER B = not provided
LISTENER B = not provided
LISTENER A = Brown

You appear to have interconnected the two devices in a manner that follows the rules. The rules for interconnecting are

RULE 1: LISTENER connects to the TALKER of the other device with the same A/B notation.

RULE 2: If a LISTENER B has no corresponding TALKER B signal, that LISTENER B connects to ground or the power source common (i.e., negative battery bus in most boats).

RULE 3: If a TALKER B has no corresponding LISTENER B, that TALKER B is insulated and left unconnected.

See my article on NMEA-0183 for more details:

http://continuouswave.com/forum/viewtopic.php?f=9&t=816

If they are not talking, there are three more layers in the onion to peel back:

--signal rate

--data being sent

--TALKER ID

I explain these in more detail at

http://continuouswave.com/forum/viewtopic.php?f=9&t=834

For more about how a radio should behave when receiving a DSC call and how it should output data about that call, see my investigation into that topic at

Data Interface in Digital Selective Calling Class-D Radios
http://continuouswave.com/whaler/ref...Datagrams.html

Chart Plotter Interface in Digital Selective Calling
http://continuouswave.com/whaler/ref...rtPlotter.html

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