Anyone tried to get DSC data OUT of Icom IC-M504 VHF?

[svlamorocha]

Hello everyone

I am trying to get the IC-M504 to send out (to the plotter) NMEA 0183 data about the other boats to talk to. Has anyone had any luck on this with this specific model of radio?

I had no luck so far. The plotters require both DSC and DSE sentences. Today today the VHF will only send out $DCRMC (which is an echo of the position it gets from the GPS) and $PICOA (which is a misterious sentence from Icom). At some point in the past I got $CDDSC (call it DSC) and only *one* instance of $CDDSE after making many calls, received position reports, etc.

The plotters are not the problem because I am reading the NMEA out data (right out of the radio) in my laptop screen with a NMEA-to-USB adapter from Digital Yacht.

Please help me save this radio because I am ready to throw it overboard.

Thanks

Charlie

[muttnik]

I have a 603 (which might be similar, but maybe not) and there's a configuration option accessed through the DSC set-up menu to say which DSC messages to output over nmea (on mine DSC->Set Up->NMEA Output). This can be switched between off, output all DSC nmea messages and output only those from stations in your DSC list (which I think is the default).

[svlamorocha]

Originally Posted by muttnik

I have a 603 (which might be similar, but maybe not) and there's a configuration option accessed through the DSC set-up menu to say which DSC messages to output over nmea (on mine DSC->Set Up->NMEA Output). This can be switched between off, output all DSC nmea messages and output only those from stations in your DSC list (which I think is the default).

Many thanks. Yes, I have the three options but the result is the same in all three of them. Could you make the thing work to display DSC targets in a plotter?

[DeepFrz]

Are you getting DSC mixed up with AIS?

[svlamorocha]

Originally Posted by DeepFrz

Are you getting DSC mixed up with AIS?

No; if you believe the manufacturer's hype you can connect your DSC radio to your plotter and see where is the guy you are talking to in a call that was initiated via DSC. AIS has nothing to do with any of this.

AlS integration with plotters and radios is a different mess altogether.

Sent from my GT-I9192 using Cruisers Sailing Forum mobile app

[DeepFrz]

Okay, did not know that. Thanks.

[ranger58sb]

Originally Posted by svlamorocha

No; if you believe the manufacturer's hype you can connect your DSC radio to your plotter and see where is the guy you are talking to in a call that was initiated via DSC. AIS has nothing to do with any of this.

Sounds like magic. My ICOM-604 sales brochure says this:

Position request and position report

Over and above the DSC, your own and other ships’ position data

can be exchanged with the position request or position report functions.

The received position information can be transferred to external

GPS or navigation equipment*. In addition, the polling

(request/

reply)

function checks whether a specific ship is within the communications

range. * NMEA 0183 format is required.

I've never bothered to try to use is, but is that what you're focused on?

-Chris

[svlamorocha]

Originally Posted by ranger42c

Sounds like magic. My ICOM-604 sales brochure says this:

Position request and position report

Over and above the DSC, your own and other ships’ position data

can be exchanged with the position request or position report functions.

The received position information can be transferred to external

GPS or navigation equipment*. In addition, the polling

(request/

reply)

function checks whether a specific ship is within the communications

range. * NMEA 0183 format is required.

I've never bothered to try to use is, but is that what you're focused on?

-Chris

Spot on.

[muttnik]

Originally Posted by svlamorocha

Could you make the thing work to display DSC targets in a plotter?

Oh this is an embarrassing confession. I don't know. When I wired it up after getting the new radio 3 years ago I went round my neighbours in the marina asking if they'd like to send me a position report or reply to a position request.

Every single one said some variation of "no: my radio doesn't do that" including a guy who teaches VHF. The *actual* deal is that very few people in the UK use DSC and only a tiny minority are aware of the DSC capabilities of their radios beyond the Big Red Button.

I moved marinas a few months back and have a new set of neighbours so will try and test this in the coming days (thanks for reminding me!)

Note also btw...I *think* I also had to explicitly enable receipt/display of DSC messages on my Raymarine C90W plotter. Check your plotter's manual to see if displays these sentences by default.

[svlamorocha]

Originally Posted by muttnik

Note also btw...I *think* I also had to explicitly enable receipt/display of DSC messages on my Raymarine C90W plotter. Check your plotter's manual to see if displays these sentences by default.

Thanks. This is on a boat with a Furuno TZT plotter that will display DSC targets by default. The techs at Furuno USA were great in running a test with their own equipment. Only trick is that the Furuno plotter requires both the DSC and the DSE sentence.

I know the plotter is not the issue because when I read the NMEA stream out of teh Icom IC-M504A I do not see any DSC or DSE messages. Instead of doing that, the bloody thing spits out echoes of the RMC or GGA position sentences that it gets from the GPS, which means you have a nasty data loop right from the start. I hate Icom when they do these things.

[ranger58sb]

Originally Posted by svlamorocha

Spot on.

Interesting.

OK, I too admit I've never tried some of this kind of stuff... mostly because I don't know too many (any?) other folks who have a DSC radio and who know how to enable position reports.

So talk me through part of it, and I'll see if I can get one of my 604s to talk to the other one.

It looks like our radios allow a manual position report entry, but I can't get excited about entering the data by hand. Given that's so unwieldly... I think the assumption must be that the DSC radio -- if polled and if enabled with a GPS input -- would be able to use the already-known position to respond to a position request? That right?

Then the corollary would be that that same response could also be formulated into a NMEA 0183 sentence for transmission on the boat's own internal network, too. Yes?

In the meantime, I'll investigate more about NMEA sentences and how to control the output.

-Chris

[svlamorocha]

Originally Posted by ranger42c

Interesting.
So talk me through part of it, and I'll see if I can get one of my 604s to talk to the other one.

In my limited experience in this sort of thing if both radios have the same MMSI (still US practice for more than one radio in same boat?) then they will not connect via DSC.

Originally Posted by ranger42c

Interesting.
It looks like our radios allow a manual position report entry, but I can't get excited about entering the data by hand. Given that's so unwieldly... I think the assumption must be that the DSC radio -- if polled and if enabled with a GPS input -- would be able to use the already-known position to respond to a position request? That right?

Correct

Originally Posted by ranger42c

Then the corollary would be that that same response could also be formulated into a NMEA 0183 sentence for transmission on the boat's own internal network, too. Yes?
-Chris

Common sense suggests that the sentence that comes out of the VHF should have the OTHER boat´s position (sentence DSC, DSE), but Icom cannot even tell when is that sentence generated (upon acknowledgement from other boat, when other boat sends unsolicited position report, etc).

Another story is that some Icom engineer withouth much marine common sense chose to make the thing spit out a carbon copy of the position sentence (say GGA, RMC,. etc) of your OWN boat that it gets from the GPS, creating one of those awful loops that drive NMEA networks crazy. This sentence comes out reliably even if it is useless.

[ranger58sb]

Originally Posted by svlamorocha

In my limited experience in this sort of thing if both radios have the same MMSI (still US practice for more than one radio in same boat?) then they will not connect via DSC.

Common sense suggests that the sentence that comes out of the VHF should have the OTHER boat´s position (sentence DSC, DSE), but Icom cannot even tell when is that sentence generated (upon acknowledgement from other boat, when other boat sends unsolicited position report, etc).

Another story is that some Icom engineer withouth much marine common sense chose to make the thing spit out a carbon copy of the position sentence (say GGA, RMC,. etc) of your OWN boat that it gets from the GPS, creating one of those awful loops that drive NMEA networks crazy. This sentence comes out reliably even if it is useless.

Umm... yes, coming to the conclusion -- about trying to "talk to myself" with the two radios -- that it's a non-starter.

A 'brochure" for the 604/604a says it puts out DSC and DSE sentences, and it differentiates between messages received from OTHER ships (DSC, DSE) and inputs from other talked on own ship's network (GGA, RMA, etc.).

My plotter says it will display data -- the transmitting ship's MMSI and position, type of call (e.g., distress), from DSC messages (but it only sites DSC sentences, not DSE sentances) received from a talker on the network.

So I think my stuff is supposed to do what you're trying to do... but I'd have to whistle up somebody here in the marina -- with a DSC radio -- to try to test all that. I'll try that, but probably won't get quick results

In the meantime... does all this mean you have spoken directly with ICOM?

Have they confirmed that they at least think your 504 should be (should have been?) sending appropriate DSC/DSE sentences? Transmitting data received from other ships?

Or do you mean they really said the DSC/DSE sentences are own ship's data, formatted only for transmission to listeners on own'ships network? (Agree: dumb.)

BTW, I found an older thread here on the Forum with intro to DSC/DSE syntax; that was interesting, albeit not perfectly complete.

-Chris

[ranger58sb]

I now have the plotter set to receive DSC data; actually, it was already turned on.

I set the 604 (the one connected to the plotter) to auto ack to all ships. (I think.)

But...

It looks like only other ships with auto ack already turned on -- or those willing to manually ack -- would respond to a position request from my 604.

And it looks like I can only poll ships whose MMSI I already know, or at least have recently received in some kind of DSC call from them.

At this point, the only MMSIs I know are a few folks around our marina (not here just now) or the ones I can see on the plotter from their AIS transmission.

I tried a couple AIS targets from the nearby Fleming fleet, but either they weren't set up to auto ack a DSC call (and didn't manually ack)... or else I couldn't tell any difference on the plotter because it was already displaying their position from the AIS info. (But the plotter didn't show the DSC icon instead of or in addition to the AIS icon.)

Rumination continues.

-Chris

[svlamorocha]

Originally Posted by ranger42c

I now have the plotter set to receive DSC data; actually, it was already turned on.

I set the 604 (the one connected to the plotter) to auto ack to all ships. (I think.)

But...

It looks like only other ships with auto ack already turned on -- or those willing to manually ack -- would respond to a position request from my 604.

And it looks like I can only poll ships whose MMSI I already know, or at least have recently received in some kind of DSC call from them.

At this point, the only MMSIs I know are a few folks around our marina (not here just now) or the ones I can see on the plotter from their AIS transmission.

I tried a couple AIS targets from the nearby Fleming fleet, but either they weren't set up to auto ack a DSC call (and didn't manually ack)... or else I couldn't tell any difference on the plotter because it was already displaying their position from the AIS info. (But the plotter didn't show the DSC icon instead of or in addition to the AIS icon.)

Rumination continues.

-Chris

Chris

1) Are the NMEA **OUT*** (not just NMEA IN) wires of your radio connected to the plotter?

2) In my limited experience I have seen that many radios will not establish any DSC communication and that squelch level may have something to do with that. Make sure your squelch is not too low for channel 71 noise level.