Do you use DSC?

Do you use DSC for making VHF calls

  • Yes - mostly

    Votes: 5 3.1%

  • Yes - regularly

    Votes: 18 11.1%

  • Seldom or never

    Votes: 125 77.2%

  • I don't have DSC

    Votes: 14 8.6%
  • Total voters
    162
Apart from distress calls, perhaps DSC is one of those great ideas which nobody realised they needed, a bit like lots of Black&Decker products used to be.
 
One of the problems is that because DSC is only used occasionally the alarms are unfamiliar. Why not increase the familiarity by calling up your friends via DSC just as they are about to turn for their pontoon, pick up a mooring, hoist a spinnaker, or whatever? You need to blag their MMSI first, though
 
Jimmyjames said:
You must also remember, the signal is digital and travels a lot further than a standard 30nm nominal VHF range so there is a better chance of your DSC being received than a voice distress message.
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How does that work?

There's no extra power in the radio and the DSC channel is only 75khz below CH16's frequency, so that isn't going to make any difference.
 
Up here even the CG don't seem to use DSC- they use ch16 for the very routine checking in of shipping making its way along the Minch. Wouldn't that be a suitable use for DSC?
 
SimonFa said:
How does that work?

There's no extra power in the radio and the DSC channel is only 75khz below CH16's frequency, so that isn't going to make any difference.
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But there is no other traffic on the channel to clog it like radiochecks on 16, microphones left on transmitting a carrier signal etc, We used to receive DSC alarms from hundreds of miles away when we were UK based, irritating at the time but illustrated that the range or signal aquisition was rather better than with voice channels.


Here in Doodle land they use DSC for buddy chat mostly it seems and the emergency transmission features of DSC are scarcely mentioned. My guess is that a high proportion of sets are not hooked up to GPS at all let alone properly and even then doubt the MMSI is correctly loaded. There are 2 ways to get an MMSI here, one is via BOAT US which is only relevant in USA waters, for international use you have to be a documented ( Like Part 1 registry) vessel to get an international call sign and MMSI issued that then goes on the worldwide database. Most seem to go the easy BOAT US route and get an MMSI online and radio voice procedure is a mix of CB radio 'good buddy' and WW2 fly boy speak copied from TV:disgust:
 
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BlowingOldBoots said:
I have just choked on my tea, considering the flak I got for carrying a liferaft. :-)

My own DSC is used like a none DSC VHF. I really should use the DSC features more.
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Ha, you are confusing intellectual discussion on the merit of life rafts with criticism of those that carry them. I stated I that thread also that I had one! :)

I also don't use the DSC features much but I think they are worth having and in my safety briefing to the crew I always explain how to push the little red button such that help will arrive.
 
SimonFa said:
How does that work?

There's no extra power in the radio and the DSC channel is only 75khz below CH16's frequency, so that isn't going to make any difference.
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Digital will get through where voice will fail, ham digital modes will go around the globe with just a few watts (different from VHF though).
Also the receivers don't have any squelch.
 
When I got my VHF cert and MMSI, it's a legal requirement to call to CG on DSC to check the MMSI No. and I had programmed several CG MMSI No.s into the radio. I successfully made the call. Moments later, A DSC alarm sounded and the CGs No. was displayed. DON'T PANIC! I called the CG back immediately, only to be told it was their all stations 1 pm weather forecast! My red face was probably visible from a dozen nm.........

I think the red button is the winner - All my guests know to press it if I go overboard.
 
Many years ago I gave an informal seminar on DSC on a club rally. This was followed by some test calls between us. Shortly afterwards, a certain lady who became our commodore heard her set's bleep go off. She picked up her handset and gave her vessel's name etc. unfortunately, she had replied to a CG urgency call. A very red face followed.
 
Robin said:
But there is no other traffic on the channel to clog it like radiochecks on 16, microphones left on transmitting a carrier signal etc, We used to receive DSC alarms from hundreds of miles away when we were UK based, irritating at the time but illustrated that the range or signal aquisition was rather better than with voice channels.
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I accept that DSC is quick and easy and less prone to error, but the assertion was that it goes further than voice.

GHA said:
Digital will get through where voice will fail, ham digital modes will go around the globe with just a few watts (different from VHF though).
Also the receivers don't have any squelch.
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Ham radio is a bit specialised. They know how to use VHF inversions and ducting, for example but they can't be relied on in an emergency. I think you're referring to meteor scatter, another mode that couldn't be relied on in an emergence.

It is also not true that, where all else eg power and antennas is equal, that digital will get through.

When the Army went digital in one area of operations in the early '80s the digital system was designed to have the same radio performance as the analogue system. What happened was that they found the the infantry, in particular, had learned to use the analogue system in ways that digital couldn't be used - one was just using PTT as a simple code as a way of communicating, something that wouldn't work with digital radios because of the roll off in performance with signal strength. They were also able to work at a lower performance ie with more noise than was generally accepted, as the minimum performance threshold needed.

A similar problem was encountered in countries that had large 1G networks when they rolled out 2G. They found they had holes in the coverage where they hadn't with analogue.

The techy explanation is that on a on a graph where the x-axis is logarithmic represents radio distance* and the y-axis represents performance the graph for analogue performance rolls off in a basically linear way, it just gets noisier and noisier and eventually you can't use it for communication. However digital performance remains constant until it gets to an avalanche point where it rolls off very quickly. Once the error rate gets above something like 1 x 10^-6** it just won't work and shuts down.

*radio distance isn't the same as radial distance at mobile phone frequencies because of reflections and refractions.

**different radios have different error correction mechanisms but IIRC 1 x 10^-6 is about right for real time digital voice systems
 
Currently it's a form of safety insurance, easy to brief, simple to use and hopefully provides the required information to the CG etc in an emergency. I think it will become more user friendly as AIS develops, in that it should be possible to call stations (CG, Marinas, vessels etc) in range by clicking a symbol or icon on a chartplotter. So, yes I do 'use' it simply by having it available for emergency use, but use standard voice procedure for routine comms. The DSC calling/answering process is currently a bit clunky.
 
SimonFa said:
Ham radio is a bit specialised. They know how to use VHF inversions and ducting, for example but they can't be relied on in an emergency. I think you're referring to meteor scatter, another mode that couldn't be relied on in an emergence.
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maybe not a great example but never mind, digital can get through when voice will be unintelligible, on ham some of the psk31 & wspr signals aren't even audible yet the data gets through.

OK it's wiki Wiki and the sources don't work but all the same,..
https://en.wikipedia.org/wiki/Digital_Selective_Calling
Because a DSC signal uses a stable signal with a narrow bandwidth and the receiver has no squelch, it has a slightly longer range than analog signals,[1] with up 25 percent longer range and significantly faster.[2].
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Kelpie said:
Up here even the CG don't seem to use DSC- they use ch16 for the very routine checking in of shipping making its way along the Minch. Wouldn't that be a suitable use for DSC?
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Pah. They (Stornoway CG) kept setting off DSC alarms last summer for utterly trivial routine information about things going on miles away. Yes, if I am on a night passage with everyone else asleep I want to know if some poor sod is sinking. I do not want to have them woken up to the thrilling information that the light on a buoy in the Sound of Luing isn't working.
 
No and I go below and turn it off when I have had 3 emergency signals for only routine traffic. I then rely on a handheld waterproof VHF which hopefully be OK to hear any emergencies that I am near enough to assist.
 
JumbleDuck said:
Pah. They (Stornoway CG) kept setting off DSC alarms last summer for utterly trivial routine information about things going on miles away. Yes, if I am on a night passage with everyone else asleep I want to know if some poor sod is sinking. I do not want to have them woken up to the thrilling information that the light on a buoy in the Sound of Luing isn't working.
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It's especially annoying when you've got a boat full of passengers and they hear the alarm and assume we're in big trouble.
 
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