DSC Position Request from Handheld with Boat's MMSI

[jboats]

Originally Posted by fairbank56

No, that's not how it works. The guy in the CG video doesn't have a clue.

Eric

Lt. Parkhurst doesn't have a clue.. ok fair enough. Apparently the USCG has been very slow on the DSC uptake so i'm not going to argue either way because I definitely don't know and look for informed sources to explain this stuff to me. It's somewhat discomforting to hear that the leaders of our military don't know WTF is going on either but not surprising. Since you seem to know more than them can you enlighten us as to WTF this guy is talking about then?

[fairbank56]

This CG video series is a joke. I couldn't believe what I was hearing when I first came across it. I had sent emails to both RadioLabs, the uploader of the youtube video's, and to the CG station that the Lt. was stationed at, complaining about this garbage. Never got a reply from either. The Lt. makes the following assertions during the video's. They are all incorrect.

DSC radio's automatically relay distress alerts from boat to boat.
DSC radio's will transmit DSC data if they don't have an MMSI programmed
DSC radio's will simultaneously transmit DSC data and voice.
The MMSI is specific to the radio itself, there cannot be two MMSI's that are the same.
You can send messages from boat to boat just like text messaging.
What consititutes a mayday/distress situation is not written policy.

The guy just doesn't have a clue, indicated both by his lack of knowledge and his mannerism and response to questions. His biggest error is stating that your DSC radio automatically relays distress alerts. Where could he possibly have gotten that information from? It is the main focus of his presentation and is 100% false.

I have seen other CG presentations out there that get it right. This is just some joker who didn't do much, if any, research on the subject. Shame on him, but now there are countless viewers of this video series that have been wrongly informed and spreading this misinformation around.

Eric

[bazzer]

So, if I receive a DSC distress call on my Raymarine 215 which can't relay what action should I take? Try the CG on 16, but if out of range should I put out a Mayday anyway in the hope that someone else might be able to relay?
Bazzer

[goboatingnow]

Originally Posted by bazzer

So, if I receive a DSC distress call on my Raymarine 215 which can't relay what action should I take? Try the CG on 16, but if out of range should I put out a Mayday anyway in the hope that someone else might be able to relay?
Bazzer

The correct procedure is to place a standard voice mayday relay call. You can proceed that with either a urgency all ships call on dsc or a coastguard dsc call. The key issue with GMDSS Over SOLAS is to get the alert to the shore station not other vessels.

If you have other forms of comms such as a sat phone that could be used to relay the distress alert to a coastguard station.

Dave

[jboats]

Originally Posted by fairbank56

I have seen other CG presentations out there that get it right. This is just some joker who didn't do much, if any, research on the subject. Shame on him, but now there are countless viewers of this video series that have been wrongly informed and spreading this misinformation around.

Eric

Please relay the links for those correct presentations.

Thanks, J

[fairbank56]

After receiving the DSC distress call, you should listen on channel 16 for 5 minutes. If the alert is not acknowledged, you hear no distress traffic and the distress call is continuing, you should first acknowledge the alert by voice to the ship in distress and then try to contact a coast station. If the alert is acknowledged by a coast station and your vessel is able to assist, also contact the vessel in distress, if not able to assist, do nothing (alert acknowledged). This comes from the Comsar flow chart for actions by ships upon reception of VHF distress alert.

Eric

[fairbank56]

Originally Posted by jboats

Please relay the links for those correct presentations.

Do your own searching. Google is your friend. This thread is months old and you obviously did not read it all before posting. I did not save the links back in November when I was looking around.

Eric

[jboats]

Originally Posted by fairbank56

Do your own searching. Google is your friend. This thread is months old and you obviously did not read it all before posting. I did not save the links back in November when I was looking around.

Eric

Then how do I know if I'm not just watching some other uninformed wannabe know-it-all spouting BS, as you have pointed out? That's why I asked; not because I was lazy.

Your right I didn't read the whole thread; I picked up at the end from a search for info on an different subject and unfortunately, I began to relay the falsehoods that I had seen in that CG video from a search for info on DSC months ago. I didn't even realize the Bad Lt. video had already been debunked by you, my bad.

Since you obviously did your own research that you feel confident about, sharing that information as links on these type of forums is how the internet was designed to work. Otherwise, mislead pleebs like myself perpetuate fallacies from ignorant "experts."

I will never trust the Coast Guard again

[goboatingnow]

Originally Posted by jboats

Then how do I know if I'm not just watching some other uninformed wannabe know-it-all spouting BS, as you have pointed out? That's why I asked; not because I was lazy.

Your right I didn't read the whole thread; I picked up at the end from a search for info on an different subject and unfortunately, I began to relay the falsehoods that I had seen in that CG video from a search for info on DSC months ago. I didn't even realize the Bad Lt. video had already been debunked by you, my bad.

Since you obviously did your own research that you feel confident about, sharing that information as links on these type of forums is how the internet was designed to work. Otherwise, mislead pleebs like myself perpetuate fallacies from ignorant "experts."

I will never trust the Coast Guard again

Of all the info floating around that particular video stands out as nonsense. Most else in my experience is OK. Knowledge of GMDSS Procedures and practices seems very sketchy in the US.

[bazzer]

This does not make sense if this the correct procedure, five minutes can be a difference between life and death. How can I relay the lat long to the next nearest down the line?

[fairbank56]

Originally Posted by jboats

Then how do I know if I'm not just watching some other uninformed wannabe know-it-all spouting BS, as you have pointed out? That's why I asked; not because I was lazy.

I will never trust the Coast Guard again

I wouldn't mistrust the CG just because one of it's officers puts out some bad information. I have nearly 37 years experience as a marine electronics service technician and hold an FCC issued GMDSS Maintainer license. I have read numerous publications with regards to DSC technical specifications and operator procedures. I immediately tested in a controlled bench test environment as to whether class D DSC VHF radio's do auto-relaying of distress alerts and confirmed what I already knew. They do not. In all my reading, research and classes, I have NEVER heard of this "feature". I know people in the CG auxillary who teach DSC classes and they have never heard of it either. It would be very interesting to know where this guy got this idea. Maybe he just made it up. He seemed to be doing just that when answering some questions. It's a shame that it is still out there. I informed the producer of the video and the CG as to the gross errors contained in it but nobody seems to care.

Eric

[goboatingnow]

Originally Posted by bazzer

This does not make sense if this the correct procedure, five minutes can be a difference between life and death. How can I relay the lat long to the next nearest down the line?

It is the correct procedure. The requirement is that you wait at least 5 minutes for the DSC distress acknowledgement to arrive from the coast guard station, before assuming it has not been heard

There is no automated way to relay lat and long in a mayday relay. All automated responses have been removed due to the problems of massive relaying of distress alerts. The simplest procedure is to make a standard mayday relay voice call, the format of that allows you to repeat verbally the position of the distressed vessel.

The key thing to remember is that you must never unintentionally provide the view that you are the vessel in distress.

GMDSS is not designed to " relay down the line". For compulsory carriage vessels, for whom the procedures are designed, are required to carry communications equipment capable of reaching a shore station DIRECTLY. Hence compulsory fit vessels with only VHF cannot operate outside Sea Area 1, ie VHF DSC range. The key component of GMDSS, unlike SOLAS is the requirement to alert the shore station directly and to carry the equipment to do so. Broadcasting to vessels in range is a secondary activity.

For non compulsory fit vessels, which find themselves outside of the range of a coast guard station, therefore simple voice procedures are best to relay such distress alerts.

Dave

[goboatingnow]

The reason it never existed, is that it can't logically work. Imagine an area like the French/Italian coast with potentially thousands of VHF DSC radios all automatically ( or even semi automatically) relaying a DSC alert potentially alerting dozens of VHF coastguard stations all requiring them to generate responding alert acknowledgements, given enough density a single alert could spread for thousands of miles, across different countries, potentially alert hundreds of rescue services.

Furthermore extend the concept into HF DSC radio, which alerts on 4 HF frequencies, potentially such a feature could cause a single alert to generate worldwide overloading.

The concept was never included in any systems produced, after the initial trial phases. Even manually initiated DSC distress relays occurs have been abandoned for the same reason, to be replaced by simple voice relay procedures.

Dave

[Admiral Cat]

Originally Posted by mikefossl

I tested that scenario several times today. My Standard Horizon HX851 handheld has the same MMSI programed as the SH GX2000 fixed mount. Position reports, position requests, individual calls all work as expected. One calls and the other answers. The GX2000 also sends the position to my Lowrance HDS chartplotter.

Great MOB solution from my perspective.

hello Mike - this post went off on a slightly different direction so I hope you don't mind me following up on your comment. I have the same radios as you, just bought the handheld and was wondering whether to use the same MMSI number for both, which ideally I would.

I think your experience confirms that I should (one radio can make a DSC call to the other and can poll the other despite having the same MMSI), there doesn't seem to be any downside to using the same number but I just wanted to check that

many thanks
Alex

[mikefossl]

Yes, I can confirm that dsc functions as expected despite having the same mmsi.