DSC Basics

[Dockhead]

This is for all the questions from the Tragedy Strikes thread.

DSC has a lot of useful functions which hardly anyone seems to use. Maybe someone will give a primer for those asking questions.

[Dockhead]

I was just going to post a link to Wikipedia or some other generic source, on the basic functions of DSC, and was surprised not to find anything particularly useful. The Wiki article doesn't even mention the routine calling functions of DSC. Maybe some CF'er Wikipaedian could rewrite it?

So I guess your radio manual is going to be the best source.

In general and in brief, the non-emergency functions of DSC are these:

1. Individual calls. Instead of clogging up 16 trying to find a particular boat or someone with a handheld, or a shore station, you can make an individual DSC call. You put in your party's MMSI (which can be stored in speed dial on most radios) and enter the working channel you want to use, and the "phone rings" on the other boat. The called parties "answers" by pressing the "acknowledge" button, and both radios are automatically switched to the chosen working channel. Pretty cool, huh? Besides other kinds of calls, I do all my radio checks like this -- calling the UK Coast Guard on DSC. My DSC system is also checked at the same time.

2. Position polling. We discussed this in the other thread. For this to work, the radio polled has to be set to allow it. You "ping" the polled radio with its MMSI, and it automatically replies with lat long. With some systems, the position is displayed on your chart plotter. Handy for a lot of uses we discussed.

3. Group call. You can set up a "conference call" by putting in multiple MMSI's. Otherwise works like an individual call.


Those are the three functions I use. Maybe someone will want to continue with the other functions.

[Rustic Charm]

I've tried several times to do an individual call to other vessels when they have popped up. It sounds like it is ringing them. But so far, no one has ever picked up on the other vessel. To date I've been thinking this is just due to it being a new thing in this area, but I'm not really sure about that.

[cal40john]

How about this-

Can You Hear M e?

[cal40john]

Originally Posted by Rustic Charm

I've tried several times to do an individual call to other vessels when they have popped up. It sounds like it is ringing them. But so far, no one has ever picked up on the other vessel. To date I've been thinking this is just due to it being a new thing in this area, but I'm not really sure about that.

The only person's MMSI I know said he could here his radio ring but didn't bother to answer.

[Dockhead]

Originally Posted by Rustic Charm

I've tried several times to do an individual call to other vessels when they have popped up. It sounds like it is ringing them. But so far, no one has ever picked up on the other vessel. To date I've been thinking this is just due to it being a new thing in this area, but I'm not really sure about that.

It hasn't caught on, even in Europe. I use it only with crew and friends. And the Coast Guard.

Sent from my D6633 using Cruisers Sailing Forum mobile app

[cal40john]

Originally Posted by cal40john

How about this-

Can You Hear Me?

All I see is a mess. The above link is the BoatUS VHF DSC tutorial, Can You Hear Me.

[nhschneider]

I am continuously amazed at how many knowledgeable cruisers are not aware of DSC functions. In the small, informal fleets we've traveled with over the last five years, we've introduced DSC to quite a few boats who often react with surprise that the feature isn't more widely used. It's appreciated by lots of people who travel with their children so the kids can call the other 'kid boats' without the rest of the fleet needing monitor their traffic - non-kid boat cruisers really like it. But, most importantly, it frees up the hailing channels for priority traffic and announcements. In addition, it gives some privacy to routine calls between boats.

What is often overlooked is the DSC feature on single side band radios. Most countries have stations where the feature can be tested and I get a good sense of security when I conduct a test and I get an acknowledgement that my signal was received. A list of those stations and frequencies can be found at KLOTH.NET - DSC - GMDSS Maritime Digital Selective Calling.

Good topic to bring up.

Fair winds and calm seas.

[Rusty007]

Originally Posted by Rustic Charm

I've tried several times to do an individual call to other vessels when they have popped up. It sounds like it is ringing them. But so far, no one has ever picked up on the other vessel. To date I've been thinking this is just due to it being a new thing in this area, but I'm not really sure about that.

It seems that most vessels broadcasting there MMSI number with their AIS transmitter do not have the MMSI number programed into there radio. If this is the case you can call some from the vessel list but they will not here the call.

[nigel1]

GMDSS which includes use of DSC was introduced way back in 1992, with final implementation in 1999. As Dockhead pointed out, the use of DSC has not been readily taken up for some reason, and this is true amongst both leisure craft and commercial vessels.
As pointed out, one purpose of DSC on VHF was to cut out unnecessary traffic on CH16, and the same with 2182kHz on SSB, which has led to the removal of the 2182 watch alarm from ships, and the shore side 2182 watchkeeping in many countries.

I have no idea why VHF DSC is underused, one theory on commercial ships is due to the proliferation of alarms on the bridge, radar alarms, AIS alarms, engine alarms etc, so that when a DSC alarm sounds, the watchkeeper may look at the message, and if it is not Distress, just hit the cancel button.

I try and use DSC, all my calls to Coastguard are initiated with DSC, and I have some luck with contacting other ships and boats by DSC, but not many.

Give it another 20 years and it may catch on.

[Sandero]

If you have two VHF.... or more.... do they each have a separate unique MMSI #?

[nigel1]

Originally Posted by Sandero

If you have two VHF.... or more.... do they each have a separate unique MMSI #?

If they are fixed VHF sets they should have the same MMSI number.
MMSI number is assigned to the boat/ship by the appropriate authority, and all equipment requiring an MMSI number will use that same number, SSB, AIS, VHF etc.

For a hand held DSC VHF radio, that will be assigned a mobile MMSI.

For UK waters, explanation can be found here
Hand held VHF DSC FAQs | Ofcom

[colemj]

Our handhelds have the same mmsi as our ship. We prefer it this way because we can receive/send calls as our ship when we are mobile. Also, we can use it as the ship primary should we lose the primary, or prefer to keep it off (lightning).

In other words, we consider and use it as an extension of our main ship radio.

If one was to use their handheld as a true independent mobile device (race committee, delivery captain, etc), then one would want a unique mmsi on it.

BTW, there is no confusion with multiple devices having the same mmsi - we can use one radio to call the others with no problem. If receiving a call, all radios ring, and answering one stops the others - with all radios able to participate in the call.

Mark

[colemj]

Other DSC functions on our radios included "all ships call", which will ring all ships in range regardless of not knowing the mmsi's. This function falls between emergency and recreational - it could be used to warn of a log adrift or something similar.

Another feature on ours is "auto polling", where up to four other mmsi radios can be position polled automatically at a user-selected interval. We've never used this, but I suppose it would be handy if traveling in company at night through sketchy areas - sort of like a targeted AIS mode without a general broadcast or use of radar.

Mark

[sailormed]

This function is called Group Monitor on my latest acquisition the HX870E from Standard Horizon. There is a Yahoo groups for this DSC/GPS VHF Hndheld. If I look at this forum many are unaware that these functions are international standards, they are surprised when they discover that "it works with a non-Standard Horizon VHF". I must say that in my marina on the Cote d'Azur there is nobody using the DSC functions of their VHF or even aware of its possibilities.