Digital Selective Calling

[sailor-d]

A while back I mentioned MMSI etc. What I really wanted to know but didn't (forgot to) include was: has anyone used DSC to call another vessel or received a DSC call and have that vessel's position displayed on a chartplotter? Personally, so far I have just not been motivated enough to wade through the technobabble in the VHF instruction manual to make use of it. Maybe at a quiet anchorage this summer the need will seize me.

An interesting (for the nosey or "just checking") url to do with MMSI, I found was:

http://www.itu.int/cgi-bin/htsh/mars/ship_search.sh

[AK Angler]

While I was attempting to connect my Uniden Polaris DSC VHF to my Garmin 178c plotter this week, I discovered, to my great dismay, that the Polaris doesn't backfeed a signal to the GPS. There is simply no provision for it. So I started poking around on the interweb and noticed that some radios do and some don't. In fact, I couldn't find any Uniden's with this capability, but I think ALL of the I-COM's do. I thought that any DSC radio would backfeed location info the the plotter... Guess I was wrong.

Anybody want to buy a barely used Uniden Polaris?

[Notayot]

I have mine connected, but have never received a DSC call. I was listening yesterday on my non-DSC portable and did hear the Coast Guard say the DSC distress system here in Port Angeles was triggered by a boat in distress, so I know the system works generally, at least here on the Strait.

[flapbreaker]

Even if you don't plan on making any "calls" if your radio is DSC capable you should take the time to hook it up to your chartplotter. If you should ever need to push the "panic button" on your radio it could expedite getting help. Especially if there are other boaters in the area who receive your coordinates. You may be the one on the receiving end of a distress call too. Don't worry if your radio won't send the incoming coordinates to your chartplotter. You will still see them show up on the radio's screen.

[Alyssa Jean]

Just a reminder that in order to activate a DSC distress call you MUST hold down the red button for at least 5 seconds. Just pushing it will do nothing.

[mikeporterinmd]

Having the radio output DSC information is useful if you want to track
friends when using DSC polling. It would also help if you did receive a
distress call. Not all chartplotters can plot information coming from all
radios.

For instance, a Lowrance unit will not plot information coming from an
Icom 422. This is because, as near as we can tell, that the Icom
emits V3 NMEA and the Lowrance only understands V2 NMEA 0183.

However, the Lowrance will emit sentances that the Icom understands,
so the Icom 422 can broadcast your position if you make a DSC call.

(Actually, it is possible a Lowrance will not plot anything coming from any
radio. Seems to be a weak area in the Lowrance. However, my old
Garmin GPS 188C had support for tracking and naming MMSI numbers,
etc. By Lowrance, I mean at least an LMS-337C DF. But, this limitation
does extend to other Lowrance units, possibly all.)

Mike

[thataway]

The Standard horizon chart plotters and radios will interphase so that the location of a boat is shown on the chart plotter. Some folks have had problems getting other brands to actually show the location on their chart plotters.

The DSC system for private calls is not dependant on the coast guard's distress calling system. There are several classes of radios. The most common just samples channel 70, instead of having a second reciever or a complete second transcever on channel 70.

[mikeporterinmd]

[oldgrowth]

David – thanks for that information. Hopefully I will never have to push that button. Now if I ever do, I hope I remember to hold it down for the five seconds to activate it.
________
Dave

[sailor-d]

From a bit of research it appears that the Icom 422 is not class D (I am not exactly sure what that really is) but may be pretty close if you set it up to dual or tri-watch and include Channel 70. The manual looks a little tedious but maybe with hands on it would make more sense.

[sailor-d]

A direct quote from the Navigation Center of the the US Coast Guard:

Class D:

Minimum DSC capability for VHF marine radios carried by recreational boaters, commercial fishing vessels, and other non-SOLAS regulated vessels. Class D required capabilities include:

* Distress call
* All-ships call
* Individual station call
* Use of distress, urgency, safety and routine priorities
* Nature of distress
* Distress coordinates
* Time for last (distress) position update
* Type of subsequent communications
* Radio VHF channel
* Display
* Receive distress relay and distress acknowledgment calls
* Alarm

It seems to me that the ICOM 422 fills all these requirements.

[mikeporterinmd]

Maybe it's a matter of looking for a seperate channel 70 receiver?

I don't know what I would really want until I receive at least one
DSC call. I live near commercial operators. I wonder if they hail
each other using DSC? Would make sense since I rarely hear a hail,
just a conversation starting up on channel 13. I'll try watching the next
time I'm on the boat.

Mikr

[thataway]

There is a discussion of the issues of the class D on Panbo today:

http://www.panbo.com/yae/archives/001592.html#more

If you really want to be confused follow his link to the discussions with
"Mr. Guntis Ositis". I suspect that "Mr Ositis" has a old reciever and is just looking for some publicity.

The best radio will have two separate transcievers--one on channel 70 and one which covers all channels separately. I generally run two radios which will do the same thing. Mr Ositis (may not be his real name) claims that most DSC radios will blank on the other frequencies when a DSC signal is recieved. He advises that one not activate the MMSI#. This is contra to Boat US, US Coast Guard etc advice.

The class D gets confusing, because it appears that some manufacturers claimed class D by US specs, with just scanning and not a dedicated reciever section. The earlier RTCM SC-101 specifications which were US specific, and not ITU (SOLAS) allowed the scanning reciever. These radios were called "Class D"

I would look for a radio which specifically has a separate dedicated full time channel 70 reciever. This radio would be ITU class D certified.

[flapbreaker]

[Gene Morris]

Sailor-d;

I have just been working on this very subject with my radio/plotter. I had a friend with a similar system set his mmsi# and we played with it a little.

I have an Icom 504 and a Garmin 3210 plotter. With my friends mmsi# in my dcs log and my mmsi# in his dsc log. I was able to call him and he was able to call me. This all happens on ch 70 and is accessed through the menu button on our radios.

First I would access dsc by pressing the menu button. Then I would decide what I wanted to accomplish, ie. private call or position report. If I wanted to make a private call I would highlight that option then it would ask me what channel I would like. Then I would transmit a call to my friends radio through his mmsi#. He would then receive a call request on ch 70 vhf. Then he would access his dcs by pressing the menu button on his radio and select acknowledge call. When he does that his radio will automatically tune to the channel that I had previously selected on my radio. Then we can talk without anyone knowing what channel we went to.

Likewise if I wanted to know his position I would ask for a position report rather than private call. When he acknowledges my request his position will be displayed on my radio and on my plotter. This is very useful while fishing or in an emergency situation.

These same functions can be used for a group of boats. Instead of having to call each boat individually it will call a group. I hope this will help and I haven't been to long winded.

Gene Morris