DSC distress relays - SailNet Community

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Go Back   SailNet Community > On Board > Gear & Maintenance > Electronics
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Old 11-12-2011
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DSC distress relays

Just want to put out an FYI about DSC distress relays. People are under the impression that their VHF DSC radio is silently working in the background doing automatic relays of DSC distress alerts. This is absolutely not the case. Class D radio's are not even capable of relay transmissions and while commercial class A radio's can do manual distress relays, there were ITU rules put in place over 10 years ago that state that in no case is a ship permitted to transmit a DSC distress relay call on receipt of a DSC distress alert on either VHF or MF channels. Unfortunately, thousands of marine radio operators and potential operators have been grossly misinformed by a youtube CG video training series stating that in fact, your DSC radio is working silently in the background doing distress relays. I just learned, and was shocked at what I heard, about this video because of this misinformation being spread on two other marine electronics forums. Unbelievable that a CG Lt. is putting this out, and this video has been out there for over 2 years now. One guy claims that he keeps his DSC handheld attached to himself so that if he falls overboard he won't have to worry because his fixed unit still onboard his boat with it's high power and better antenna will relay the distress call to the CG. Not going to happen. It is total BS.

Eric
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Old 11-12-2011
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I never suspected that my DSC radio was retransmitting signals. Guess I didn't see the vid. Want to post the link?
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Old 11-12-2011
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VHF Marine Radio - DSC Radio USCG- Pt. 1 - YouTube

The guy clearly doesn't have a clue as to what he is talking about. His presentation and answers to questions are full of misinformation.

Eric
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Old 11-12-2011
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Quote:
Originally Posted by fairbank56 View Post
vhf marine radio - dsc radio uscg- pt. 1 - youtube

the guy clearly doesn't have a clue as to what he is talking about. His presentation and answers to questions are full of misinformation.

Eric
Wow! I had a customer trying to tell me this summer that DSC equipped radios will "pass on" or relay a call. I explained it does not work that way, automatically, and he swore the USCG told him so. I brushed it off as strange but now I know the poor guy probably saw that video or spoke to a coastie who also believed that..

I think people need to make more comments on that video so the USCG deletes it or edits it until it is portraying correct information.
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Last edited by Maine Sail; 11-12-2011 at 07:23 PM.
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Correct me if I am wrong; if your DSC equipped VHF is connected to your GPS, the GPS will display the location of a received DSC call? I thought I read that in my Icom manual.
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Old 11-12-2011
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While DSC radios may not relay distress calls, I did hear about a call that seems to have riccocheted a good distance somehow. The distress call, from a commercial fishing vessel in the Gulf of Mexico, was received as a "squawk" on a DSC radio... in New Jersey. The owner checked the set, but there seemed to be nothing within range. He was about to turn off the radio and drive home when it went off again. He took down the ID number and called the coast guard. They tracked it to the boat's location in the Gulf of Mexico and apparently pulled three guys off the boat before it sank. Strange things can happen.
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Old 11-13-2011
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Quote:
Originally Posted by mdbee View Post
Correct me if I am wrong; if your DSC equipped VHF is connected to your GPS, the GPS will display the location of a received DSC call? I thought I read that in my Icom manual.
IF your VHF has data output, some don't. IF your GPS is capable of receiving DSC data, some older models don't. IF the received DSC call contains position data. Not all DSC communications do.

Eric
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Old 11-13-2011
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So if you have the handset on your vest and fall off send the signal your fixed set onboard will recieve the location, is that not where help would go.
In a MOB situation it would be prudent to turn your fixed unit off then if single handed ???
Or would possibly two blip location be recieved, thus showing a skipper at one and the boat at a second, the faster being the boat on continued location req's.

Also if you have two handsets would you get both location from them to your fixed unit. Example, one of my kids takes our daysailor and is out passed the marina where I cant see, and my other is in the dink fishing round the bens again where I cant see, if I loc req'd would both hand sets come back with locations.
I am told my CPV350 can show location readings.
just trying to get a better handle on this and looking to really put some of the comments into usage this season, thanks to all for great info.
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Quote:
Originally Posted by KnottyGurl View Post
So if you have the handset on your vest and fall off send the signal your fixed set onboard will recieve the location, is that not where help would go.
No. The fixed set will only receive your distress call, it will not transmit a position or anything else. If your handheld has built-in gps, your position will go out with the distress call. If not, you will have to enter it manually. If somebody receives your distress call without position and they do a position request, and your fixed unit is set to auto-ack, then they would get the boat position.

Quote:
In a MOB situation it would be prudent to turn your fixed unit off then if single handed ???
No

Quote:
Or would possibly two blip location be recieved, thus showing a skipper at one and the boat at a second, the faster being the boat on continued location req's.
They will only get a response to a position request if you have your units set to auto-ack. If both handheld and fixed are set to auto-ack, then we have the problem of both trying to respond at the same time.

Quote:
Also if you have two handsets would you get both location from them to your fixed unit.
Good question. You might receive one, both, or neither. Both would receive the position request at the same time. If they are both set to auto-ack, they would both try to respond at the same time. If one has a stronger signal it will "capture" the receiver in the fixed unit and get through. If equal strength, neither may get through. If one starts transmitting a split-second before the other, will the other one wait til the channel is clear or do they just blindly start tranmitting on the channel? I don't know. Worth experimenting with.

Eric

Last edited by fairbank56; 11-13-2011 at 10:36 AM.
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Thanks fairbank56 makes sense, I am getting new handhelds so lets say the hx model mentioned that does have gps with dsc. Its the location acknowledge that is throwing me off. I sailing lake Ontario so CG is somewhat close on both sides and handhelds will recieve Rochester CG.
So we have to assume new HX model will have same reception.
As I singlehand most of the time what would be the case in this situation as for MOB.
I see the power aspect but both could send the acknowledge and both should do be recieved by station. How would this test be accomplished, contacting both Prescott and Rochester to ask for dsc distress test from my mmsi number
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