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Old 01-02-2019, 09:57   #1
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GPS signal to icom M302

Firstly I have searched for answers on this and the info found so far is more confusing than if I had not found the threads.

So my new boat has a Icom M302 and two loose wires that are for a GPS input. I am also fitting a Raymarine tridata instrument that uses a SeaTalk cable for its power supply. My current understanding is if I get some sort of GPS data onto my SeaTalk bus then I can breakout a couple of wires and send them to the VHF so I can use itís automated functions....?

A quick google brings up the Raymarine RS150 ($250) unit that looks like it will provide the gps functionality I need...?

Is there a more economical way of achieving this because I can eBay a vhf with built in GPS for similar price...

Please excuse my ignorance in these matters Iíve had a tough first two weeks of boat ownership...! And I think Iím going to have a couple more as well.

Regards Steven
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Old 01-02-2019, 10:23   #2
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Re: GPS signal to icom M302

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Originally Posted by Steven UK View Post
...new boat has a Icom M302 and two loose wires that are for a GPS input....
You may find useful information in an article I wrote about a similarly old ICOM radio, the M402. See

ICOM IC-M402 Radio Rehabilitation
ICOM IC-M402 Radio Rehabilitation - CONTINUOUSWAVE
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Old 01-02-2019, 10:46   #3
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Re: GPS signal to icom M302

I have an M304 radio which is probably pretty similar. I used to take the NMEA0183 directly from my plotter at 4800 baud (if your raymarine network is SeaTalkNG then you can't do this cheaply), but then when I added an AIS receiver I had to configure the plotter for 38400baud, but the radio couldn't handle that. So I made a simple arduino based GPS which cost about $25, and it keeps the radio happy ... if you're not happy making your own then an old used garmin handheld with an nmea output will probably be the cheapest option.

But to be honest, I never use the GPS based functions of the radio ... I suppose if I ever lift the red flap and push the mayday button, I'll be happy it has a gps signal. But if you've only had the boat two weeks ... I'd push this waaay down the list of jobs that need doing, there's probably more important things to keep you awake at night.


edit: That RS150 you linked is a SeatalkNG (NMEA2000) device ... this will not be compatible with the NMEA0183 data input on your radio ... you would also need to add something like an Actisense adapter (another $200) to make the conversion.
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Old 01-02-2019, 21:29   #4
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Re: GPS signal to icom M302

No you can not just break out nmea 183 wires from a seatalk or seatalkng (more likly what you have) network.

If you buy a chart plotter. Get one with nmea 183 to feed the radio. If you have no intentions of getting a plotter. A new vhf with gps would be easiest.
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Old 02-02-2019, 00:33   #5
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Re: GPS signal to icom M302

Get the raymarine seatalkng to nmea0183 converter for less than $100. Designed specificaly for feeding gps data to a vhf or ssb radio
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Old 02-02-2019, 11:33   #6
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Re: GPS signal to icom M302

The OP asked for an economical solution. For $20 he can buy a new, marine GPS receiver with NMEA i/f and 12V power, from China:
https://www.aliexpress.com/item/12V-...807433645.html

For $6 more he can buy a unit that also receives GLONASS, and if he wants to do a little extra work, Galileo. Or GPS+Galileo+(Beidou or GLONASS): https://www.aliexpress.com/item/NEW-...971734254.html
The only downside is that it takes 1-2 months to receive.

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Old 05-02-2019, 06:44   #7
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Re: GPS signal to icom M302

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Originally Posted by CarinaPDX View Post
The OP asked for an economical solution. For $20 he can buy a new, marine GPS receiver with NMEA i/f and 12V power, from China:
https://www.aliexpress.com/item/12V-...807433645.html

For $6 more he can buy a unit that also receives GLONASS, and if he wants to do a little extra work, Galileo. Or GPS+Galileo+(Beidou or GLONASS): https://www.aliexpress.com/item/NEW-...971734254.html
The only downside is that it takes 1-2 months to receive.

Greg
Perfect...! Thanks. Iím sure this will help more than just myself.
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Old 05-02-2019, 11:29   #8
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Re: GPS signal to icom M302

You're welcome.

I recommend getting the Galileo-capable one; Galileo is comparable to GPS for accuracy while the GLONASS service is not quite as good. To program it for Galileo either do it with the U-blox Windows app or, better, the current version of GPSd (v3.18) on a Linux system (the capability to configure a U-blox 8 was just added). With the NMEA interface you will need a serial port, best done with an RS-422 to USB adapter but the typical RS-232 interface should work.


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Old 05-02-2019, 11:29   #9
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Re: GPS signal to icom M302

Steven, and more importantly for others looking on here...

1) For the past 15 years, I (and many others) have been recommending using a separate, dedicated GPS to feed NMEA position data to your DSC radios, both VHF-DSC and MF/HF-DSC...

Quote:
Originally Posted by Steven UK View Post
Perfect...! Thanks. I’m sure this will help more than just myself.
Of course, I've been touting the use of Garmin portable GPS units (like my Garmin GPS76's / GPSMAP76's), as this allows you to use these as position displays at your Nav Station, or even in your dinghy, or ditch-bag...

But, whatever separate GPS unit you choose (I'm not too keen on the cheap Chinese pucks, due to possible QC issues), they allow you to get NMEA 0183 position data direct into your DSC radios, no matter what else might be operating or not operating (failed?)...

I've never understood the desire to run a chart plotter when out on the open ocean....of course if approach land, islands, etc., sure.....but on a multi-week passage, I hear of people running their plotters 24/7?? And wonder why?? and wonder how much electrical power they're using??
All you need it a position plot / running fix / log entry, every few hours, and plot that on a chart (paper chart or even just a log book)....so just take your position off a GPS display (or radio display, since you're likely to have the VHF-DSC-FM radio on 24/7)....
This saves you a lot of electrical power!! And, gives you one more tool in your kit!



2) If you're interested in an overview of VHF-DSC, please have a look at this Youtube Playlist...

VHF-DSC
https://www.youtube.com/playlist?lis...J6QugtO2epizxF



3) If you'd like to see how I've utilized a dedicated GPS...have a look.....
Note I replaced the old Garmin 76 with a newer GPSMAP76 and have a few "spares" on-board, too...(one for dinghy, one in ditch-bag, and one mounted here at Nav Station....giving lots of redundancy/options)...they are powered from the ship's 12vdc system (but also are able to work all day on two AA batteries), and send NMEA 0183 position data to both my M-802 and M-602 DSC radios....I use the Garmin 12vdc/data cable (~$10) and a Garmin panel-mount (~ $15) for mounting the unit on the Nav Station panel....
{been this way now for about 15 years...been across the Atlantic a few times, thru a tropical storm at sea, numerous Gales at sea, and three Cat 3 Hurricanes at anchor....never an issue...}












4) And, fyi....one of my videos (the first video in the "Offshore Weather" Playlist), explains an "offshore" / "voyaging" boat's approach to Nav Station layout and design....you might find this interesting, too...

Offshore Weather
https://www.youtube.com/playlist?lis...zdjTJjHlChruyY


{Also, look at video #3 in the HF-DSC Playlist....to see how/what is switched on, etc....and how it all works...}

If you desire more info on HF-DSC, the Icom M-802, Offshore Sailing, Maritime Hf comms in general, etc...have a look at these too..

HF-DSC
https://www.youtube.com/playlist?lis...ga2zYuPozhUXZX


Icom M-802 Instruction Videos
https://www.youtube.com/playlist?lis...rC-8QKVyMb4tVr


Offshore Sailing (just fun on some Atlantic crossings)
https://www.youtube.com/playlist?lis...KgTCj15iyl6qoY


Maritime HF Comms in general
https://www.youtube.com/playlist?lis...ZDo_Jk3NB_Bt1y



Hope this helps some...

Fair winds..

John
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Old 05-02-2019, 11:56   #10
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Re: GPS signal to icom M302

Quote:
Originally Posted by ka4wja View Post
Of course, I've been touting the use of Garmin portable GPS units (like my Garmin GPS76's / GPSMAP76's), as this allows you to use these as position displays at your Nav Station, or even in your dinghy, or ditch-bag...

... (I'm not too keen on the cheap Chinese pucks, due to possible QC issues)
There is no quality problem with these units. All modern equipment uses standard GPS modules; u-Blox is a leading brand but there are others such as Sirf. These external GPS units are nothing more than a module, antenna, and DC-DC power supply for 12VDC - USB (5V) goes straight in. My brother is one of the principle GPSd devs and has literally dozens of GPS modules, mostly purchased direct from China, operating and monitored continuously. Quality is simply not an issue, at least with the modules. Of course there are occasional firmware and software issues but the modules are pretty bulletproof.

The old Garmin units still work just fine; they are not quite as accurate, energy-efficient, or quick to acquire first fix but for everyday use you will likely not notice it. If you have them and are happy then keep on trucking... OTOH if you are looking to buy then a VHF with GPS would be a better investment for standalone battery-powered use. Or do as I do and use a tablet or smartphone as a backup. Or a laptop with a USB GPS unit from China. GPS (and other GNSS receivers) are a commodity today and should not cost much. These multi-hundred dollar branded marine units are absurdly expensive and no better than my Chinese units - in most cases they are a generation or more behind in technology (but still locate well).

Greg
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Old 05-02-2019, 12:17   #11
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Re: GPS signal to icom M302

Greg,
Perhaps my wording was too strong?

I didn't mean to offend....just to say that I personally don't recommend them for this particular application....

I find some modern, mass-produced, DC-DC converters, etc. to have QC issues....and for this application (safety / distress) I'd rather have a more reliable and proven track record behind them, especially since the added cost is about what you'd pay for a nice dinner out...

Now, in defense of the Garmin units....yep, from a cold start, after being powered off for a few weeks, it does take them about 30 to 45 seconds to find a fix (Sirf III, I think??)...so, while in an extreme emergency every second counts...but, in this application (where they run 24/7 while I'm out sailing), this is a moot issue for me...

And, the fact that I've still got an old GPS76 (~ 15 years old) that has spent many a month in my dinghy, floating in salt water and/or exposed to Florida / Caribbean heat, and the darn thing still works perfectly!!
I don't care if it takes a minute to find a fix, from a cold start....I still like it..
But, to be clear, I do NOT use that old unit anymore at the Nav Station or ditch-bag....it's relegated to the RIB now....


And, yes....I suppose the older units won't get a GLONASS or Galileo fix??...And the WAAS position might not be quite as accurate as the newer units, but I'm not using 'em to navigate a tight harbor entrance in zero-vis, so if they're within +/- a few meters that's plenty accurate for this application...


So, to sum up....I'm sure one of the less expensive Chinese modules will work....but, I personally am not yet willing to recommend them...
But, that is just my opinion...


Fair winds.

John
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Old 05-02-2019, 14:22   #12
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Re: GPS signal to icom M302

John-
Perhaps my wording was too strong as well. We are just talking - all is good.

We agree that even the old units have utility for just knowing the position. Unless you're like me and like living at the bleeding edge there really is no good reason to "upgrade" GPS receivers. Our disagreement is with the cheap Chinese units, where you have a concern about quality and I don't. In the last few years I personally have been through about a dozen GPS units, NMEA and USB, and my brother would be closer to a hundred, with no quality issues. Also, I don't recall ever having heard of failures of such devices, other than by water intrusion to non-waterproof units, or lightning strikes. In other words, it is just not a problem. YMMV, but if not based on experience then consider rethinking that.

As I wrote before, upgrading doesn't buy much. Newer units are more sensitive and so don't need to be outside to pick up a good selection of satellites. In a permanent install an outside antenna is not an issue anyway, but operating a handheld device down below can be an issue with older technology. Time to fix, cold, warm or hot start, is improved but mostly doesn't matter. Power consumption is reduced, which is a win for handheld devices, but there it is the device's total features that matter, not just the GPS module. As for the improved accuracy (mostly a result of being able to counter propagation issues), it is still not possible to count on finding your slip blind: 95% of the time yes, but that other 5% can be off tens of meters, even with today's best consumer and marine units. The expensive services used for surveying, etc, use two or more bands to get a better fix. The next generation of u-Blox modules will have dual band, but are still a ways out. With the current u-Blox 8 the receiver evaluates available info and then uses the satellites that are best, of the systems selected. With GPS-GLONASS-Galileo selection it will choose GPS and Galileo satellites but will evaluate and not use the GLONASS ones. On the west coast Beidou isn't common enough for me to have a feel for; I guess in Asia it does contribute so better to have that instead of GLONASS. Still, for navigation accuracy is not really a concern. The commercial needs driving the accuracy are autonomous vehicles, where the accuracy needs to be sufficient to identify the highway lane 100% of the time - not there yet.

Because of my interests, and my awareness of developments through my brother, I like to keep up with technology. I source units from China, then sell on my old ones. My most recent switch involved selling a u-Blox 6 and replacing it with a u-Blox 8, with support for all 4 worldwide GNSS systems. Still, my chartplotter and radios each use old SirfStar III (Globalsat mushrooms) - why not? They work. I might upgrade to the u-Blox 9 on the chartplotter in a couple fo years, which would be about 6 generations ahead of what I have now, for a small win, but I don't think most cruisers would find upgrading worth the effort.

BTW for about $15 one can buy a puck with a u-Blox 8 module and a compass and accelerometer inside; the problem is that they have an i2c interface for use with autonomous drones. If they were available with an NMEA interface it would be nice as they do a pretty good job of dead reckoning. Also, outside of the established marine brands ($$$) it is hard to find any modules with N2K interfaces - I think someone is missing a bet here.

Greg (KF7BW)
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Old 07-02-2019, 04:59   #13
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Re: GPS signal to icom M302

Guys two equally good solutions to the same problem, my local marine liquidator has some Garmin OEM 17n which outputs in NMEA 0183 which is the same as the icom M302 for $50. This along with my plan to buy a gps enabled handheld vhf should cover the bases mentioned above. I have nothing against the Chinese parts mentioned above but I cannot plan my location 1 to 2 months from now. Thanks for the enlightening info, iwouldent have spotted the Garmin OEM17n on the if I had not read the posts above.

Regards Steven
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Old 12-03-2019, 07:22   #14
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Re: GPS signal to icom M302

Little more information... I have ordered one of these (see photo below) and a 5v dc-dc power supply. Iím planning to get the icom M506 because of its AIS functionality (I sail singlehanded) but it also needs a gps input same as the M302. Iím sure this can be connected because of the quantity of anecdotal info. Does anyone have experience in connecting this unit to NMEA 0183 or 2000, I know just enough about canbus systems to be dangerous...
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Old 12-03-2019, 08:10   #15
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Re: GPS signal to icom M302

Quote:
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...experience in connecting this [GlobalSAT BU-355S4, the unit under discussion but never actually identified] to NMEA 0183 or 2000, I know just enough about canbus systems to be dangerous...
Not likely to be useful with NMEA-2000. It probably sends NMEA-0183 serial data. If the default serial port settings are proper, it could be easy to integrate.
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