DSC Call function via Chartplotter via NMEA 2000 or 0183

[tanglewood]

Originally Posted by goboatingnow

Strange mine seems to work

So you can press a button for an AIS target on your chart plotter and it causes the VHF to initiate a DSC call to that AIS target? And earlier you said it was a Raymarine chart plotter and an SH 1850 VHF? Are the two interconnected via 0183 or N2K?

[tanglewood]

There are two parts to this, so important to be clear what we are talking about.


Incoming DSC calls, especially emergency incoming calls, have standard 0183 sentences and N2K PGNs. As a result, any reasonably modern connected VHF and plotter should display incoming DSC calls on the plotter.


In the other direction, there is nothing standardized in N2K, but there is in 0183. What I think many of us would like to do is click on an AIS target on a plotter or radar, then click on a "call" button to initiate a DSC call to that boat. Without this, DSC is pretty much useless for placing calls because you have to enter in the target's MMSI using a horrific user interface on the VHF. Predictably, nobody uses it. The big problem is that at least in N2K, there are no define PGNs to initiate a DSC call, only PGNs to receive DSC calls. To the extend this does work, it's the result of proprietary PGNs that some vendor defined for their own use.


0183 is different because it does define a sentence to initiate a DSC call. But I don't think it's widely supported by VHFs or plotters.

[flightlead404]

Originally Posted by Witte C

I’ve learned over the years we humans have become so complex with technologies that we are unable to successfully implement everything created to a level of our expectations. Simple systems are usually most reliable and implemented easily.

The problem is with standards bodies being made up of employees of the large vendors and so being largely powerless, and with the vendors themselves who agree to give themselves a pass to create proprietary protocols so they can claim compliance but still force you to purchase the entire suite of electronics from a single vendor to get it to work.

[Tehani]

Originally Posted by tanglewood

In the other direction, there is nothing standardized in N2K, but there is in 0183. What I think many of us would like to do is click on an AIS target on a plotter or radar, then click on a "call" button to initiate a DSC call to that boat. Without this, DSC is pretty much useless for placing calls because you have to enter in the target's MMSI using a horrific user interface on the VHF. Predictably, nobody uses it. The big problem is that at least in N2K, there are no define PGNs to initiate a DSC call, only PGNs to receive DSC calls. To the extend this does work, it's the result of proprietary PGNs that some vendor defined for their own use.

0183 is different because it does define a sentence to initiate a DSC call. But I don't think it's widely supported by VHFs or plotters.

This has also been discussed in this thread:

https://www.cruisersforum.com/forums...ml#post3471425

[stevead]

I think this question can be distilled into four elements.

1. Does the radio have the ability to initiate a VHF DSC call via a NMEA 183 or NMEA 2000 interface in addition to its control panel ?
2. If it can, does that radio use standard NMEA 183 sentences or NMEA 2000 PGN's ?
3. Does the chartplotter support such functionality ? Eg. Click on a DSC or AIS target and then allow the user to initiate a VHF DSC Call, Poll Request or Position Request ?
4. If the chartplotter supports such functionality, how does it recognize the presence of a compatible VHF DSC radio ? Does it just assume a radio is present ? If it is NMEA 2000 does it use PGN 60928 or PGN 126996 or a proprietary PGN to recognize the presence of a radio and/or does it only recognize radios made by the same manufacturer as the chartplotter.

In the case of NMEA 183, I can confirm that an Icom VHF DSC radio can initiate VHF DSC calls via standard NMEA 183 sentences.

For example:
Individual Call (requesting the station to accept a call on VHF Channel 69)

$CDDSC,20,0022410240,00,00,26,900069900069,,,,R,*28

Poll Request

$CDDSC,20,0022410240,00,03,26,,,,,R*07

Position Request (Requesting the station to respond with its position)

$CDDSC,20,0022410240,00,21,26,,,,,R*07

All Ships (Alerting "All Ships" to listen on Channel 72 for a Safety Message)

$CDDSC,16,,10,00,26,900072900072,,,,R*03

I have never tried (for obvious reasons) to initiate a DSC Distress Alert !

To understand the NMEA 183 DSC sentence refer to the NMEA 183 standards document. To understand the parameters refer to the ITU publication "Recommendation ITU-R M.493-15"

I do not know whether other brands of NMEA 183 equipped VHF DSC radios offer the same levels of support over NMEA 183, or whether they use proprietary NMEA 183 sentences.

Similarly I do not own a VHF DSC radio with a NMEA 2000 interface, so I am unable to confirm whether a similarly crafted PGN 129808 message will initiate a VHF DSC Call.

However I have received a few candump logs from NMEA 2000 equipped VHF DSC radios and can confirm that Icom radios emit standard NMEA 2000 PGN 129808 messages upon receipt of a VHF DSC Individual Call, Poll Request, Position Request and All Ships call.

If other users are interesting in investigating this further (Eg. Sending the above NMEA 183 sentences to other brands & models of NMEA 183 equipped VHF DSC radios or capturing logs and sending messages to NMEA 2000 equipped radios) then please send a PM or email to twocanplugin at hotmail dot com

[Captain Bill]

An interesting academic discussion. In the 15 years I have had DSC capability on my radios absolutely no one has answered a DSC call that I had not made previously made arrangements with by voice. Big ships have never answered a DSC hail, though I have tried many times. The same ships answered voice hails on 16 immediately. Other than prearranged boat buddy stuff I have only once seen anything useful using DSC. In that instance I was coming out of NY city about 2 miles south of the narrows when I received a DSC distress call from a boat off of Atlantic City, NJ. After not hearing a voice response from the CG for about 10 minutes I hailed the CG and asked if they had received the call. They had not. I relayed the position data to them from my DSC call log. They located the craft with a failed engine about 20 miles NE of Atlantic city. It was also the only DSC distress call I ever received that was not a false alarm. My take on this for the OP is just hail the vessel by name on 16 and not waste your time and effort trying to make a DSC call or trying to fix the issue.