DSC Radios

[poggy]

Hi,

I've been thinking of a DSC radio and was curious about how and if all DSC radios can receive the distress signals from other DSC units and how it is displayed.

Thanks

Poggy

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[Jools_of_Top_Cat]

as part of the short range vhf training it now includes DSC, if you already hold the vhf most schools will lets you do the few hours part just to get the dsc.

Will answer all your questions, and give you the license.

I hold the license but not have a dsc set, would like one, but while my vhf still going strong cannot justify the costs of a new set.

<hr width=100% size=1><font color=blue> Julian </font color=blue>

<A target="_blank" HREF=http://www.ukstaffords.com>http://www.ukstaffords.com</A>

 

[tony_brighton]

What you get on receipt of a DSC mayday is:
- a very loud audible warning
- a display statement giving the MMSI and position of the victim (if GPS hooked up - not much point otherwise!)
- nature of distress if the victim has time to input (usually they are equiped with a standard drop-down list e.g. fire, flooding etc)

All DSC radios should pick up a mayday if in range - its part of the standard maritime safety procedures.

Personally I would not go back to a non-DSC radio. The benefits of pressing the red button and having your position transmitted far outweight any other concerns.

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[snowleopard]

DSC distress

You'll certainly know about it if your DSC picks up a distress call. the noise is deafening and the call data appears on your screen.

Unfortunately, as with all automatic alarms, a fair proportion of these alerts are false alarms. I picked up one and spent the next hour on VHF and SSB trying to do a mayday relay. eventually the dopey git caught on to what had happened. he was in a marina and didn't have his GPS switched on so the message had no position data.

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[poggy]

Hi,

The thing that worries me about just having DSC with the coastguard giving up a dedicated watch on 16 is that digital communication requires a good signal. In most cases of course DSC provides a huge amount of information at the touch of a button and can only add to safety, especially as it transmits the location and boat details to everybody in range.

I may be corrected as I know very little about DSC but if you have a electrical problem, the GPS will more than likely fail and on most VHF sets if the power is disturbed the memory of the last GPS location will be lost. Also DSC is digital and in my experience of running a broadcast equipment manufacturing company, if you don't get a good signal you don't get anything. With analogue although you may get noise etc, you can quite often get the message across. I know that following a DSC message being received the coastguard will try and contact the vessel on CH16, but what if they don't receive the DSC.

Surely DSC is a great additional benefit which should be adopted by everybody, but is a dedicated watch on 16 not also still quite relevant.

Poggy


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[Gunfleet]

You also get the message delivered to every ship in the area. There's no guarantee they will be listening to Ch16. In fact, with DSC I don't really listen to Ch 16. It's on there, but I don't listen to everyone else's quacking and if the engine is on I can't hear it. However the audible tone for gale warnings, maydays and the like from the coastguards certainly gets my attention.

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[Mike_Martin]

Hi Poggy,

I shouldn't answer this, as the tech spec of the GMDSS is MCA territory. I would suggest dropping the MCA a line.

However, some things that should be highlighted.

A: The idea of the GMDSS and the trial of it began in 1974 and I have never heard of the problems that you mention occuring.

B: DSC in NOT just about "DISTRESS" calling, all calling is done on C70, with C16 assuming role of Distress & Safety Working only.

C: This isn't just a UK thing and many Merchant Men already do not monitor Channel 16. It's worth bearing in mind that quite often it's a ship other than Coastguard/RNLI that will come to your aid.

D: I can't find a techie to confirm this at the moment but roughly speaking, DSC is not the same as DAB. The idea of DAB is to allow better quality of broadcast while constricting bandwidth to allow more broadcast services, whereas DSC fits a digitised burst of information into the existing bandwith. However, I have heard that it may well allow the data to get to the end of the signal without dropping off into the noise before the signal reaches its target as can occur with voice.

Mike

<hr width=100% size=1>Manager,
Aeronautical & Maritime Services Section,
Radiocommunications Agency

 

[poggy]

Hi,

Thanks for the info.

Just as well it's not like DAB or I would be a bit worried, given my experience of DAB reception as a consumer.

I will have to go on a DSC course and get the add on to my licence, it obviously offers a lot of extra's such as the gale alerts etc.

This is probably a stupid question which will be answered when I do the course, but if you spot a ship and would like to call it up, how do you do this if they are not listening out.

Thanks for your help.

Poggy

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[pandroid]

I suspected this too, however I asked the Coastguard about it and they find the reverse. For some reason, they often get DSC alerts when they cant get voice (or get voice at weak strength - their kit shows them instantly the strength and bearing of any voice transmission)

I put it down to the fact that modulation is probably high on CH70 and the signal has some error checking in it, so it gets through.

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[Mike_Martin]

Hi again,

Yes this should be answered on the course, although I am beginning to have my doubts since the MCA/RYA shortened the course because pleasure boat owners complained about the cost.

At the end of the day it is hard to properly cover all of the details involved in the GMDSS in a day. When I went over to the SRC (about 4 years ago) I took the old/proper 2 day course and it opened my eyes up to the new system fully. From what I've heard about the 1 day version it doesn't cover all the little wrinkles but it is cheaper so that's alright then.

However, the answer to your question is:

If it is a SOLAS vessel, they ARE DSC enabled and they WILL be watching C70, they even have 2 separate antennas to ensure that this is so. They can be raised with a Safety call/All Stations followed by your safety message on 16, in the usual way ie a "Securite".

If it is a "Voluntary Fit" (pleasure craft) vessel, things start to get shady (at the moment) but the above will still apply. The problem is that you can't guarantee that the radio is even on, let alone monitoring C16 or C70.

If you are non-DSC things are a little harder but you would still put out the Securite on C16 and if you were looking at a Merchant Man bearing down on you, you would also call on C13. C13 is the Bridge to Bridge Safety channel and it should be monitored where a "danger of collision exists" and you can tell him how you are going to avoid his "stand-on" tanker etc.

Mike

<hr width=100% size=1>Manager,
Aeronautical & Maritime Services Section,
Radiocommunications Agency

 

[charles_reed]

It\'s lovely isn\'t it..

you can panic to your heart's content - and hope not too many have been contempt'd thro' familiarity as has snowleopard.

Seriously tho' most MRSCC are not keeping even a loudspeaker watch - relying on an auto alarm for Mayday and Pan-pan.

It took Cap Gard 53 minutes to come back to me the last time I had occasion to put out a call.

So if you want your squawk to be heard you have to be on DSC.

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[byron]

<font color=blue>It would have been so much easier if things had been left alone and 16 was the calling and distress channel. DSC enabled vessels could have been tuned to send out on that channel. Now we have 16., 70 and 13. where before there was just one channel.

<hr width=100% size=1>http://www.alexander-advertising.co.uk

 

[charles_reed]

Au contraire

Digital signals are more effectively received under mediocre transmission conditions, because missing bits can be "rebuilt" in the reciever.

It is true that when conditions get too bad for a meaningful signal they drop out - but an analogue signal is useless for any meaningful understanding at the same point.

The listening watch on Ch 16 has already been extended twice - in fact UK CG are far more tolerant than most other international MRSCC bodies.

The decision was taken (I believe) in 1982 to phase out "Sparks" and listening watch, and the Ch 16 was due to be stopped in 1996, but was extended to last year and has now had another extension.

Because DSC is based upon 1970/80s technology, it is both expensive in hardware and inefficient in practice.

However Mon am' the decisions were already taken, probably before you started sailing!!

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[charles_reed]

Ch 13

It's not too bad in N European waters, you can usually raise someone on Ch 13, but in the Med, where there are probably more close-quarters' incidents, it's almost impossible to get any reaction, especially soddin' Moroccan ferries.

So I'm afraid I wouldn't depend too much on Ch 13, or a watch on Ch 16.

God I wish we still had Very pistols, a flare across the bridge always used to work wonders.

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[charles_reed]

Superfluity of channels

But nobody could hear anyone because there was too much attemepted traffic on the few available.

No doubt Mike can enlighten us on when the next vhf channel "split" will occur (and we'll have x2 the channels you're now used too) and how much narrower marine radar beams are going to have to be (so that governments can balance their books by selling further bits of the electromagnetic spectrum to over-optimistic GSM operators).

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[bedouin]

Re: Au contraire

I thought the UK still provided a dedicated headphone watch on Ch16 (until end of 2005 was it?) and then would switch over to loudspeaker only "indefinitely"

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[charles_reed]

You\'re right

I've just checked with Falmouth - they will be keeping a dedicated headphone watch until Dec 2005.

No wonder they're feeling a bit sore about these whingeing yotties, they've had to endure the manpower reductions the DSC was supposed to bring and provide the service.

Quite uniquely alone are HMCG.

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[Birdseye]

Re: It\'s lovely isn\'t it..

i found that i didnt get a response to a dsc call to cross etel for some considerable time - at least 10 minutes, and i never got a response from the spanish equivalent. ok , neither of these calls were emergency, but it seemed that response was slower than to a call on 16.

and the uk coastguard have several times come back on 16 with "will the station calling on dsc please identify themselves". not my set - some sort of problem with handling dsc calls and cross relating with the mmsi database at their end.

probably still worth doing since it will come right in the end, but its not right now for sure.

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[Jools_of_Top_Cat]

Re: It\'s lovely isn\'t it..

Just to continue this thread, what you have written interests me. I did the GMDSS course last year and I thought the course was a little hazy on routine calls to the coastguard or river controllers etc.

Also I have not purchased a dsc set yet, I am not sure if they are used much up ere in tha north. Do you now always call the CG on DSC, do you then choose the working channel so if he replies it switches his set to the channel of your choice.

Does he later say, call you via DSC, or is the system still being played with in real life, do you use the DSC capability very often, do many friends have sets installed.

I am struggling to justify the purchase, basically, right now, is it worth the extra expense?

<hr width=100% size=1><font color=blue> Julian </font color=blue>

<A target="_blank" HREF=http://www.ukstaffords.com>http://www.ukstaffords.com</A>

 

[charles_reed]

DSC

On vhf - Ch 70 - digital calling only with a pre-set message on TX only available when you press the panic button.
Otherwise Ch 70 is RX only.

All subsequent casualty voice traffic is on Ch 16.

Ch 16 is still (theoretically) used as the ship-to-shore communication inception channel. For this reason it should have a loudspeaker watch kept on it.

Only UK MRSCC are still keeping a dedicated headphone watch on Ch 16,until 2005, all the others have, I believe, changed to DSC.

Ship-to-ship collision-avoidance communication is on Ch 13 - a continual watch is supposed to be kept on it, more observed in its breach in my estimation (perhaps you shouldn't judge by Medierranean standards).

If you haven't got DSC and are in UK waters, I'd keep a dual watch on 16/13 and ensure I upgraded to DSC in the next 2 years.
Elsewhere if you haven't got DSC rely only on God and yourself for your preservation.
(A 406/121.5 EPIRB is handy for immediate pre-mortem communication with the rest of the world).

I'm investigating upgrading my elderly Mc Murdo personal EPIRB (battery change is due) to a 406/121.5 personal one. Beware the cheap 121.5 EPIRBs on the market, many are only designed as a local (to boat) man-overboard locator with an RDF station on the boat. Not much good when you're a single-hander.

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