USCG Marine Safety Alert re DSC Distress Alert Calls

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
jimh
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USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 12:53 pm

In September 2011 the Coast Guard of the United States of American (USCG) issued Marine Safety Alert 04-11 (full text available via the hyperink). Although it has been more than four years since this alert was issued, I don't recall hearing about it or hearing much reaction from boaters to it. I just happened to come across the alert this morning. I am a bit surprised by what the USCG has said. Here are two excerpts:

First, the alert contains a warning to mariners that their "...SAFETY [is] ENDANGERED WHEN VHF RADIO DISTRESS ALERTS BY DIGITAL SELECTIVE CALLING (DSC) LACK LOCATION AND IDENTIFICATION INFORMATION."

Then the alert delivers what I find to be a surprise:

As the Coast Guard’s new marine radio network Rescue 21 becomes operational throughout the
U.S., rescue centers can now receive instant distress alerts from commonly used DSC-capable VHF
marine radios. However, approximately 90% of VHF DSC distress alerts received by the Coast
Guard do not contain position information, and approximately 60% do not contain a registered
identity. The Coast Guard cannot effectively respond to a DSC distress alert sent from such a radio.

This means that search and rescue efforts may normally be suspended when:

• no communications with the distressed vessel can be established,

• no further information or means of contacting the vessel can be obtained from other sources, and

• no position information is known.


I guess mariners are now on notice: if you send a distress alert with a DSC radio that lacks location and identity information, the USCG may suspend its search for you if the three conditions set forth above are met. What comes as a surprise is the notion that no position information could be obtained unless you sent it in your DSC distress alert message. The Rescue 21 radio network provides excellent direction-finding capability, and it should be able to provide a reasonable position fix for the origin of a distress alert message sent by DSC, even though the transmission duration is rather short. I believe the radio direction finder facilities of Rescue 21 can get a radio bearing on transmissions that are very short duration, measured in milliseconds. [UPDATE: the problem with Rescue 21 is the direction finding receiver is monitoring the voice distress channel, 156.800-MHz or Channel 16. It is not monitoring the DSC channel, 156.525-MHz or Channel 70.]

The USCG Navigation Center website, on the webpage related to special notices and alerts for digital selective calling (DSC) also mentions Marine Safety Alert 04-11.

I guess I have been overlooking this notice for four years. Now that I have become aware of it, I think it is proper to spread the word on this alert. The crux of the alert is to inform boaters that you really ought to get your digital selective calling (DSC) radio connected to a position finding device (like a GNSS receiver or a chart plotter with a receiver built-in) and to properly register and use an maritime mobile service identity (MMSI). Otherwise, the USCG might not really go to the max to find you in an emergency.

The alert comes from the office of the assistant commandant for marine safety, security, and stewardship. I don't know if that office sets official policy for rescue operations, but their warning is a bit ominous. I also find it curious that the alert is said to have been "[d]eveloped by the Spectrum Management and Telecommunications Policy Division (CG-652), United States Coast Guard Headquarters, Washington, DC." Again, I wonder if those guys are in charge of rescue policy.

In any case, the smart money as a recreational boater is to get yourself a DSC radio, get a proper MMSI, and interface the radio to a position finding device. Don't be part of that 90-percent of boaters sending DSC distress alert calls with no position information and for who the USCG may suspend its search.

porthole
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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby porthole » Sun Mar 13, 2016 1:16 pm

I guess you can look at this several ways.

First, I thought you had to have a MMSI number programmed into your radio to even use the DSC panic button?

Second, if I have my radio programmed and not interfaced with position information and I send out a channel 70 DSC distress signal, the USCG may decide to not look for me? Hopefully they will still broadcast a [Marine Assistance Request Broadcast].

Third, I could just call a Mayday on channel 16 and assets will be launched, good chance I will be searched for and [Marine Assistance Request Broadcasts] will be transmitted for several days.

Unless I am completely mistaken.
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jimh
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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 1:38 pm

porthole wrote:...I thought you had to have a MMSI number programmed into your radio to even use the DSC panic button?


The DSC radios that conform to the latest recommendations probably won't operate in DSC mode at all unless an MMSI has been entered, but the report from the USCG that 60-percent of the DSC distress alert calls they had received as of c.2011 had no MMSI must mean that a lot of existing DSC radios can make a distress alert call without an MMSI.

Conformance to the newer specifications for DSC radios has been in effect since March 2011. Hmm, let's see: from March 2011 to September 2011 is six months. I guess you could say the USCG waited for a period of six months from the FCC time they banned manufacture, importation, sale, and installation of older DSC radios to make their announcement about their rescue policy regarding DSC distress alerts without MMSI identities.

Here is the notice about cessation of manufacture, import, and sale of non-compliant DSC radios:

http://www.navcen.uscg.gov/pdf/gmdss/DSC_Notice.pdf

Curiously, the notice also says "...previously-installed radios meeting the older standard may continue to be used."

By the way, the latest recommendation for DSC radio behavior is RECOMMENDATION ITU-R M.493-14. (The one in effect in 2011 was the dash-11 version.) The recommendation regarding operating the radio without an MMSI is give in section 12.4:

12.4 Maritime mobile service identity

DSC equipment should not transmit any DSC call until own ship’s MMSI allocated to the ship by the
relevant administration has been configured and stored in the DSC equipment.


I have not bought any newer DSC radios nor have I tested them for conformance to the recommendation above.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 1:44 pm

porthole wrote:...if I have my radio programmed and not interfaced with position information and I send out a channel 70 DSC distress signal, the USCG may decide to not look for me?


Yes, that seems to be what is said in Marine Safety Alert 04-11. Are you as surprised as I am?

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 1:47 pm

porthole wrote:...I could just call a Mayday on channel 16 and assets will be launched, good chance I will be searched for and [Marine Assistance Request Broadcasts] will be transmitted for several days...Unless I am completely mistaken.


Considering the policy that seems to be suggested in Marine Safety Alert 04-11, making a voice transmission on Channel 16 with a MAYDAY call might be a good back-up plan to any DSC distress alert call that lacks an MMSI or position information.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby porthole » Sun Mar 13, 2016 2:12 pm

[Re entering an MMSI into a DSC radio} my older Icom M402 manual states:
The 9-digit MMSI (DSC self ID) code can be programmed at power ON.
This function is not available when the MMSI code has been programmed by the dealer.
This code programming can be performed only 2 times.


My Standard Horizon GX-2200 specifically mentions the MMSI must be programmed to use the DSC features. And the blurb about programming the MMSI
WARNING--The MMSI can be inputted only once. Therefore please be careful not to input the incorrect MMSI number. If you need to change the MMSI number after it has been entered, the radio will have to be returned to Factory Service. Refer to the section “17.2 FACTORY SERVICE.”


[ASIDE to Porthole on the tangential subject of how often a boater can change the MMSI of a DSC radio: the GMDSS committee is seeking a change to make it simpler for the boater to modify the MMSI of the radio. We can pursue this topic in another discussion--jimh.]
Thanks,
Duane
2016 World Cat 230DC
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1997 Outrage 18, Yamaha 125
1983 15 SS, Honda 50
1980 42 Post
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porthole
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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby porthole » Sun Mar 13, 2016 2:23 pm

My older Icom only puts the distress call out with position info and then switches the radio to 16 for you to make the real call [i.e. a voice MAYDAY]. With the Standard Horizon GX2200 I can broadcast the nature of my distress [Undesignated, Fire, Flooding, Collision, Grounding, Capsizing, Sinking, Adrift, Abandoning, Piracy, or MOB], providing I am not too distressed to poke through the menu to bring up the correct nature of distress.

jimh wrote:Are you as surprised as I am [about Marine Safety Alert 04-11]?


Yes I am.
Thanks,
Duane
2016 World Cat 230DC
1999 Outrage 21, Yamaha SW Series II 200
1997 Outrage 18, Yamaha 125
1983 15 SS, Honda 50
1980 42 Post
1983 34 Luhrs 340 SF

jimh
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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 2:47 pm

Well, that makes two of us. Maybe we are the first two to read this alert. I am also very surprised I haven't read anything about it before this.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 2:57 pm

Re older radio behavior with DSC features: there is a lot of variation among older radios which complied with the much older standard from the Radio Technical Commission for Maritime Service, Special Committee 101 (RTCM SC-101). This standard was really only used in the USA. It was recognized as a way to get lower-cost radios to have DSC features by providing a simpler standard for them to comply with. Later, the CLASS-D standard was created for lower-cost radios. For the past five years new radio behavior has been more uniform and should adhere to the ITU-Rec. M.498-11 I cited above. It really does not matter how older radios behave because:

--we can't change how they behave, and

--the USCG already announced they can continue to be used.

That they work differently than new radios is to be inferred by the change in regulations. If the new regulations did not require different behavior, there would be no point in having new regulations.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Sun Mar 13, 2016 3:13 pm

Another surprising aspect of Marine Safety Alert 04-11: it refers to the Rescue 21 system becoming "operational throughout the U.S." in that September 2011 alert. The USCG just announced that the final coastal Rescue 21 facility was completed only a year ago, in February 2015.

The Rescue 21 system is still being deployed in the "Western Rivers" segment at this moment. The USCG announced an award to the contractor for that portion of the system just six months ago in August 2015. The project is not expected to be finished until 2017.

It seems a bit strange that in 2011, six years before the full deployment of Rescue 21, the USCG would begin to alert boaters the USCG may discontinue searching for them if their DSC distress alert does not have position or information data.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Mon Mar 14, 2016 5:04 pm

Upon some further investigation into the operational characteristics of RESCUE 21, I discovered the primary direction finding antenna receiver is dedicated exclusively to the voice emergency channel, 156.800-MHz or Channel 16. This configuration cannot be changed by the operators. It is dedicated to Channel 16. That means no Rescue 21 site would never get a direction finding line of bearing on a DSC transmission on the primary system.

There is a secondary direction finding channel that can be tuned to other channels, but the normal procedure is to leave it on 157.100-MHz or Channel 22A. The tuning of the secondary channel is only available to users with administrator access. On that basis the chance that a Rescue 21 site could get a radio direction finding line of bearing on a DSC transmission on their secondary direction finding system is extremely small and to the point of being more or less unlikely to ever happen.

The effect of this combination of boater negligence in making a DSC distress alert call without sending a position, and even more negligence to not even send any identification, along with the operational use of Rescue 21 direction finding facilities to literally almost never be monitoring the DSC call channel (156.525-MHz or former Channel-70), has very serious consequences. It means that a boater is likely not doing themselves anything helpful by sending a distress alert via DSC without an MMSI or position. They would be much farther ahead to make a voice call on Channel-16, even if they just yelled MAYDAY for a few seconds. At least from that transmission the USCG would get a line of bearing to the transmitter making the MAYDAY, and there would be a very good probability that more than one Rescue 21 station would pick up the transmission, thus producing a position fix solution. In that situation the USCG would have, at least, a position for the location of the transmitter sending the voice MAYDAY call, which is more than they can get from a botched DSC distress alert without position or MMSI.

If a DSC distress alert is made with an MMSI but no position, the USCG would know the name of the boat and other information, assuming it was properly registered. But with no position, all they'd know is that the vessel registered to that MMSI was declaring a MAYDAY.

Again, it really comes down to the boater taking some responsibility and properly setting up their VHF Marine Band CLASS-D DSC radio so that it can send the boat position from the boat GNSS receiver, and send the actual boat identity in the form of the MMSI. If a boater has an older DSC radio with no MMSI entered and no position data provided to the radio--but one that still permits a distress alert to be sent--then hitting the red distress alert button is not going to get help there fast, and, with the provision of Marine Safety Alert 04-11, maybe no help at all if the USCG can't follow up with the boat in some other form of communication.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby Hoosier » Tue Mar 15, 2016 10:15 pm

One thing now happening to deal with this problem is several radio manufacturers are building a GPS receiver into the radio. The big problem with interfacing the radio to a chart plotter has been a large number of boaters have no idea how to do it. However the boater still has to be responsible enough to get an MMSI and to program it into the radio.
1978 Outrage V20 with 2004 Suzuki DF-115. 1992 23 Walkaround with two 2010 Yamaha F-150s.

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Re: USCG Marine Safety Alert re DSC Distress Alert Calls

Postby jimh » Wed Mar 16, 2016 10:56 am

In retrospect, the introduction of VHF Marine Band radios with DSC capabilities that permitted use of the EMERGENCY button to send a distress alert message without a position and with no MMSI was a profound mistake. (These radios are described as RTCM SC-101 type DSC radios.) The USCG has reported at one point in time--this was prior to the mandate to change the Class-D DSC radio behavior--that 90-percent of the DSC distress alert calls it had received contained no position data and 60-percent contained no MMSI. This is a terrible misuse of digital selective calling and the distress alert call function.

To speculate on the mindset of most boaters--the 90-percent and 60-percent of boaters mentioned above--those boaters must have been seriously mislead by their purchase of a radio with a big red button for sending a distress alert, and they thought all they had to do was push that button to get help. What they really got when they bought those radios was a distress alerting system with some assembly required. The boater had to assemble and integrate his own final system by connecting the radio to a position finding device (like a GPS receiver).

To connect the radio and the GPS receiver, the only practical method was to use NMEA-0183 interconnection. As we all know (from reading endless requests for help on making these connections in on-line forums), making the interconnection is far from easy. The USCG sent the NMEA organization a letter--you might say a polite request--that NMEA do something to fix this problem, to make the interconnection of radio and GPS receiver using NMEA-0183 easier. The response from NMEA seems tepid. I think all they did was to propose to update NMEA-0183 to a new version 4.0 and to restate their preferred wire insulation color coding scheme. This has been mostly ignored by the actual manufacturers of marine electronics. Marine electronic manufacturers continue to produce equipment with NMEA-0183 interfaces that do not provide the required differential electrical signals, to label these signals with non-compliant and confusing names, and to not comply with the color code recommendations.

The FCC stepped in and stopped the importation, manufacture, sale, or installation of new DSC radios that were not DSC CLASS-D compliant, but then the USCG said it was alright to keep using the older DSC radios if they were already installed.

The USCG apparently decided it would bring some attention to this problem in 2011 by sending out Marine Safety Alert 04-11, but I don't think this alert has gotten much notice from boaters. It is likely there is still a large fleet of recreational boaters out there with RTCM SC-101 radios who think they are going to get attention and aid if they push that big red button.