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Old 11-07-2016, 02:21   #166
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Re: DSC Basics

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Originally Posted by Rustic Charm View Post
Sounds like how my wife drives a car. Ignoring lights in the dash.
You knew what mattered and what you could ignore....

A centralised alarm panel within reach of the 'seat of command' would have been a nice touch.
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Old 11-07-2016, 02:30   #167
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Re: DSC Basics

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Originally Posted by El Pinguino View Post
So... does it make the same racket when receiving a routine non urgent call ..ie from another yacht?
Noises are different, but both of them are loud and annoying.

And just as you described -- typically undesignated distress from bloody Ushant which goes off just as you are trying to get her alongside on a stormy night, and really need to be able to hear your crew's shouts about how many meters or centimeters are left before contact with the quay Sod's law. Actually happened on multiple occasions.

I've gone from using the helm second station to cancel the alerts to using the helm second station to simply shut down the radio as we start our harbor maneuvers
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Old 11-07-2016, 05:01   #168
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Re: DSC Basics

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Originally Posted by Blue Crab View Post
Radio check, radio check, radio check ... can anyone hear me?
Yeah, there is that.... <sigh>... Sea Tow's automated radio check system (channel 27, in this area) is nifty. If people would use it, it'd be even niftier.


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Originally Posted by Rustic Charm View Post
On my Standard Horizon with inbuilt AIS, I just select one of the ships coming up on the AIS and then I can hail them using 'DSC CALL' and it's meant to be as simple as that.
I've heard of capabilities like that. Our network doesn't support it; wish it did...


Quote:
Originally Posted by El Pinguino View Post
Anybody here know what noise their DSC makes when a 'call' comes in?
Ours -- at least for DSC distress calls -- apparently uses the same alarm mechanism/sound that a VHF weather alert causes. Either is loud enough to wake the dead. Very easily distinguished from all the other alarms that could go off on our bridge...

-Chris
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Old 02-02-2017, 07:01   #169
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Re: DSC Basics

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Originally Posted by gamayun View Post
Well, this brings up an interesting question to me and that is: What if a boater who receives a DSC alert some ways offshore determines that he is really close by, so he acknowledges the distress, and then goes over to help -- say pluck an MOB out of the water. Everyone is shaken up, cold and wet, but fine; now what happens? Would a CG helicopter fly over to check things out if they did not get an answer, particularly if the boaters are out of VHF range?
I was taught not to acknowledge a DSC distress alert as acknowledging the alert cancels the alert. My sense is cancelling the alert should be left to the controlling station. Best to transmit a Received Mayday on 16 to the vessel in distress and lend assistance if such assistance can be accomplished without placing your vessel in danger. If the CG did not respond to the vessel in distress initiate a Mayday Relay call (on 16). The CG might be out of range of the distress vessel but not your vessel. If the CG did respond then you want to keep them advised of your actions.
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Old 02-02-2017, 13:59   #170
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Re: DSC Basics

Don B, et al,
While this is a very good thread (and I again thank Dockhead for starting it!), the question here regarding what to do if you receive a DSC Distress Call, is quite old (from January 2016), and was answered here in this tread the very next day after it was asked, and addressed in detail....as well as putting to rest the myth that DSC radios "relay" your distress call (they do not!)

But, perhaps it is worth answering this again, as some that are new to this discussion might not be aware...
Quote:
Originally Posted by gamayun View Post
Well, this brings up an interesting question to me and that is: What if a boater who receives a DSC alert some ways offshore determines that he is really close by, so he acknowledges the distress, and then goes over to help -- say pluck an MOB out of the water. Everyone is shaken up, cold and wet, but fine; now what happens? Would a CG helicopter fly over to check things out if they did not get an answer, particularly if the boaters are out of VHF range?
This was answered the very next day....the procedure was described and flow charts posted shortly after that....
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Originally Posted by ka4wja View Post
if we receive a DSC Distress Call, and it continues without acknowledgement for 5 minutes [we are monitoring the corresponding Voice channel/freq, as well as waiting for a DSC Acknowledgement], then we should acknowledge this DSC call by VOICE on the associated VOICE frequency, NOT via DSC!!!
And, immediately notify the relevant RCC / Coast Station to our reception of a Distress call and telephony/voice acknowledgement, AND ONLY THEN acknowledge the Distress call ourselves via DSC, ONLY if directed to do so by the RCC / Coast Station
Although I learned "3 minutes" from the USCG (rather than the "5 minutes"), that was over 15 years ago, and they didn't have DSC infrastructure in place as of then....so....
The procedure is well laid out by the IMO in the GMDSS plan, fairly easy to follow, and if followed it works quite well! (I've actually done this myself, in the real world on HF-DSC....12577.0khz DSC and 12290.0khz HF-SSB Voice...)

In the scenario described in the question above, if the rescuing boater was in range of a coast station, but perhaps the person/vessel in Distress was not (?), and not hearing an acknowledgement, the rescuing boater notified the authorities / coast station, while waiting the prescribed 5 minutes, prior to acknowledging the DSC Distress Alert, via Voice Radio (what the officials call "telephony"), such as on VHF channel 16 if this was a VHF-DSC Alert (or if this was a MF-DSC or HF-DSC alert on one of the GMDSS MF/HF-SSB Voice channels, such as 2182, 4125, 6215, 8291, 12290, or 16420khz), then the rescuing boater and surviving MOB should NOT expect a visit from some SAR asset (USCG Helo, if within USCG Helo range)....BUT...
But, if the rescuing boater was farther away from a coast station than the vessel in distress, and/or out-of-range of a coast station, and not having another means of notifying the authorities, it IS possible that you would get a visit from some SAR asset (USCG helo, merchant vessel vectored to that position, etc.)...AND...
And, this is why the procedure is for you to notify the requisite authorities (coast station, coast guard, RCC, etc.) that YOU are close and that you are able to assist, and to wait 5 minutes before responding to the DSC Distress Alert yourself...
But, if the proper procedure was followed, then the rescuing boater would have also contacted the relevant authority (such as USCG) by some means (VHF, MF, or HF radio, satcom, etc.) to advise them of the situation, and would have gotten direction to acknowledge the Distress Alert, probably via Voice call....(possibly via DSC, but ONLY if directed to do so by the requisite authorities!)



There are some here that eschew the flow charts, because they are designed to be used by professional mariners (using commercial Class A radios, which may have some features that our consumer Class D radios do not), but the flow charts can be useful to some that prefer to learn visually rather then reading the text here...

You can decide...here are the procedures to follow:

First, in simple English:
If we receive a DSC Distress Call, and it continues without acknowledgement for 5 minutes [we are monitoring the corresponding Voice channel/freq, as well as waiting for a DSC Acknowledgement], then we should acknowledge this DSC call by VOICE on the associated VOICE frequency, NOT via DSC!!!
And, immediately notify the relevant RCC / Coast Station to our reception of a Distress call and telephony/voice acknowledgement, AND ONLY THEN acknowledge the Distress call ourselves via DSC, ONLY if directed to do so by the RCC / Coast Station (and of course, only if our radio is capable of doing so, which it most likely is not!)




Now the Flowcharts:
First for VHF-DSC (and/or MF-DSC):



And, then for HF-DSC:








Don B, you are correct that a Distressed Vessel's DSC radio will stop transmitting a DSC Distress when it receives a DSC Distress ACK, but our consumer-marine Class D VHF-DSC-FM (and Class E MF/HF-DSC-SSB radios) don't have that capability to send a DSC-Distress Acknowledgement call (commercial, GMDSS/SOLAS-grade, Class A radios do), so we aren't capable of stopping the vessel in distress radio from sending it's DSC-Distress call...
If we respond to this other vessel (acknowledge their distress) and offer assistance, it is up to them (at their discretion) to cancel their DSC-Distress call, or not (and wait for the authorities to respond)...
{I was told almost 15 years ago, that some early consumer-grade versions of marine DSC did have this DSC-Distress ACK transmit feature, but I've never seen one...but, regardless, if the proper IMO/GMDSS procedures are followed, all does work...}
Quote:
Originally Posted by Don B View Post
I was taught not to acknowledge a DSC distress alert as acknowledging the alert cancels the alert. My sense is cancelling the alert should be left to the controlling station. Best to transmit a Received Mayday on 16 to the vessel in distress and lend assistance if such assistance can be accomplished without placing your vessel in danger. If the CG did not respond to the vessel in distress initiate a Mayday Relay call (on 16). The CG might be out of range of the distress vessel but not your vessel. If the CG did respond then you want to keep them advised of your actions.



Anyone wishing to read all the details....have a look...
https://www.navcen.uscg.gov/?pageName=cgcommsCall

https://www.navcen.uscg.gov/pdf/marc...SS1_Circ17.pdf
http://msi.nga.mil/MSISiteContent/St...17chapter4.pdf
https://www.navcen.uscg.gov/?pageName=DSCClasses

http://www.gmdss.com.au/images/pdf/25.pdf

http://www.gmdss.com.au/images/pdf/vdscflow.pdf
http://www.gmdss.com.au/images/pdf/mdscflow.pdf
http://www.gmdss.com.au/images/pdf/hdscflow.pdf



Hope this helps clarify things...

Fair winds.

John
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