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Old 11-12-2007, 11:59   #1
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DSC marine VHF & MMSI?

It's time for a new marine VHF radio and I'm reading about DSC. There seems to be two distinct classes of radios out there for pleasure boats. The more expensive type has two independent receivers in it. One of them constantly monitors marine VHF channel 70 for DSC messages which utilize the MMSI number assigned to your boat while the other receiver is what we are accustomed to.

The less expensive radios have but one receiver and I think they ignore the DSC channel 70 completely unless you have the radio parked on that frequency, but then again, all of us would have the radio on channel 16.

Both types can send an emergency DSC message and can provide location during an emergency if the radio is connected to a GPS.

My question is the obvious one. For a guy who seldom uses the radio at all is it worth paying $100 more for the more complicated radio? Has anyone used the DSC messaging on channel 70?

Any input would certainly be appreciated.
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Old 11-12-2007, 12:43   #2
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In my opinion, the extra price isn't worth it...

DSC is still in it's infancy and we've never come across cruisers that use it.

Be aware however that certain Uniden VHFs monitor Ch 70 and if there's any signal on it, will misbehave. This caused a lot of folks problems here in Mexico where Channel 70 is still often used for Voice and not dedicated to DSC.

I'd recommend ICOM or Standard Horizon radios, not Uniden.

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Old 11-12-2007, 15:59   #3
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I believe that the cheaper DSC VHF radios listen to 70. The difference is when you are actively listening to another channel, as in squelch is broken, your one receiver is busy with that channel and will not hear the call or distress signal.

Picture the radio you have now on scan. If someone is talking on 68, you don't hear any of the other channels you are scannning. Only when 68 is released does your radio check the other channels again.

Go to page 2.
http://www.usps.org/national/safety/...tinFeb2007.pdf

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Old 11-12-2007, 16:10   #4
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The website below answers a question that you made me think of. Some articles said that there is a class of DSC can receive while you are transmitting which didn't seem right at first glance. Since there are radios that can do this, I would think that they will have a separate antenna for channel 70 that has to be mounted away from the other antenna.

Go to the section equiping your boat, then classes of DSC radios.
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Old 11-12-2007, 16:58   #5
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In years of cruising and tens of thousands of miles we have met NO ONE that uses DSC either cruising or locally.
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Old 11-12-2007, 17:02   #6
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John

Thanks for the links. I've done a fair amount of reading on the technical differences between the Class D and the SC101.

What I was wondering is who really needs all the bells and whistles? More importantly, do I need them? Hence my post.

Chuck -- I hear ya but if your're going to buy a radio these days it's going to have one type or the other of DSC. I guess a specific question you might be able to answer is if VHF cruisers' nets are going to group DSC calling? Right now, I just can't think of another application for this stuff. OTOH, it would just be my luck to buy the SC101 radio and find out later what I missed out on.

Bill, thanks for the tip on Standard Radio /vs Uniden. I see that Standard Radio is discontinuing the MATRIX GX1280S and it looks like a bargin. I particularly like the idea of a knob to change channels. Yes.... I know I'm showing my age when I say that.

Anyway, anyone have any thoughts on SC101 (less expensive) vs Class D radios?

Just an aside but this from the US Coast guard website:

The USCG plan to implement GMDSS Sea Area A1 is one element of the USCG National Distress and Response System Modernization Project, now called "Rescue 21", which replaces the whole USCG VHF distress system.

On 24 September 2002, Secretary of Transportation Norman Mineta announced the award of this $612 million contract to General Dynamics Corp. Until this system is installed, the Coast Guard cannot reliably receive VHF DSC distress calls.

US Coast Guard DSC-Equipped Shore Stations Station
CAMSLANT Chesapeake VA MF/HF -- 003669995
COMMSTA Boston MA MF/HF Remoted to CAMSLANT 003669991
COMMSTA Miami FL MF/HF Remoted to CAMSLANT 003669997
COMMSTA Belle Chase LA MF/HF Remoted to CAMSLANT 003669998
CAMSPAC Pt Reyes CA MF/HF -- 003669990
COMMSTA Honolulu HI MF/HF Remoted to CAMSPAC 003669993
COMMSTA Kodiak AK MF/HF -- 003669899

It would appear that even the basic DSC emergency broadcast from a vessel will fall on deaf ears for the most part.

You'd think that 5 years would be enough time to buy a few radios...Sheesh..
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Old 11-12-2007, 17:48   #7
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We have not found any cruisers nets that use group DSC so not sure where they might be. Most nets are outside the US and channel 70 is used as a working channel in most other countries. Because most don't use DSC and don't even have an MMSI number they would not be able to participate in a DSC group net leaving a large percentage of the anchorage out of the net.
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