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Old 13-03-2012, 19:27   #1
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VHF with DSC - Mayday

Hello all,

Recently purchased a VHF with DSC and AIS. Got a question:

If a Mayday situation arises, what should I do first:
-Call "Mayday" on Channel 16 OR
-Press the DSC distress button

Thanks
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Old 13-03-2012, 19:30   #2
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If you can the requirement is both

in an emergency ( defined as grave and imminent danger)

Activate the DsC distress alert ( preferably a designated distress alert)

Follow up with a voice mayday call on ch16

Dave
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Old 14-03-2012, 16:15   #3
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Re: VHF with DSC - Mayday

Have you programmed an MMSI number into the radio? If not, you cannot send a DSC distress alert. I highly recommend that you obtain an MMSI and connect a GPS to the radio to fully enable the DSC function.

Eric
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Old 14-03-2012, 16:44   #4
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Re: VHF with DSC - Mayday

Quote:
Originally Posted by fairbank56 View Post
Have you programmed an MMSI number into the radio? If not, you cannot send a DSC distress alert. I highly recommend that you obtain an MMSI and connect a GPS to the radio to fully enable the DSC function.

Eric
Agreed, note your GPS must be on for the radio to get the location to send.
Note Push the button first it sends an alert and sends the info to all the others radios in range. Also sets off an alert on there boats to listen
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Old 14-03-2012, 21:17   #5
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Re: VHF with DSC - Mayday

Hello,
Thanks for the input - it's as I expected.
Yes I have a MMSI number and a GPS hooked into the VHF.
So 1st press DSC button, then go to 16 and listen/transmit.....

Thanks!
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Old 14-03-2012, 21:31   #6
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Re: VHF with DSC - Mayday

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Originally Posted by aroett View Post
Hello,
Thanks for the input - it's as I expected.
Yes I have a MMSI number and a GPS hooked into the VHF.
So 1st press DSC button, then go to 16 and listen/transmit.....

Thanks!
You should get an acknowledgement of the DSC call. Then establish comms on 16.
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Old 14-03-2012, 21:41   #7
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Re: VHF with DSC - Mayday

dsc tutorial

Can You Hear M e?
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Old 15-03-2012, 03:51   #8
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Re: VHF with DSC - Mayday

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Originally Posted by cal40john View Post
dsc tutorial

Can You Hear Me?
Nice Link Cal40john, thanks for posting it
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Old 15-03-2012, 06:21   #9
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Re: VHF with DSC - Mayday

Then go for the epirb , if you have one!
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Old 15-03-2012, 07:56   #10
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Re: VHF with DSC - Mayday

Quote:
Originally Posted by aroett View Post
Hello,
Thanks for the input - it's as I expected.
Yes I have a MMSI number and a GPS hooked into the VHF.
So 1st press DSC button, then go to 16 and listen/transmit.....
Thanks!
Big NO, NO on the underlined & bolded part. Manually switching your radio to Ch 16 after you have initiated (pressed the DSC Distress button) a DSC distress call - will CANCEL your DSC distress call.

You got a manual with your radio and need to read the chapter on DSC operation several times to get a clear understanding of what DSC is and how it operates on your brand of radio. If you did not get a manual, you can normally download one from the radio manufacturer's website.

On some brands of DSC equipped radios you need to lift the protective cover, then depress and hold the DSC Distress button for up to 5 seconds before the feature is activated. On other brands it activates immediately.

But on all brands of radios, a DSC Distress call when activated will broadcast a distress command on Ch70 and then it waits for an acknowledgement from somebody's radio (which could be the USCG if you are in range of a USCG station). If an acknowledgement is not received by your radio within 4 to 5 minutes your radio will then retransmit the DSC Distress call automatically.

If you manually re-channel your radio, you will cancel the DSC Distress call.

When an acknowledgement of your DSC Distress call is received by your radio, your radio will automatically re-channel itself to channel 16 - you do not have to touch anything.

There are several different "levels" of DSC Distress calls, but the basic one of depressing and holding the covered Distress button will send a Distress message with your MMSI number and GPS location from the GPS you have attached to your radio. Everybody who has a DSC equipped radio turned on and within reception range of your radio will hear a very loud "siren" type sound from their radio. Then all the receiving DSC radios will automatically re-channel to channel 16. To stop the loud "siren" you normally just have to depress the microphone button. On some radio's depressing the "CALL" button will also turn off the "siren."

You then can use your microphone to to talk to whomever responds to your Distress Call first.

There are several different "levels" of DSC Distress depending upon your brand of radio. These are known as "Nature of Distress" and can be selected from your radio's menu. Some "Nature of Distress" categories are "flooding," "collision," "grounding," "explosion," etc. Your manual will list them.

- - -
The DSC function of your radio has other features besides the "Distress" function. It also can be used to send an "All Ships" message - similar to a "Pan, Pan" message.

And, best of all, it can be used to establish contact with a "buddy boat" without having to make a public broadcast to attempt to call your "buddy boat." This feature operates similar to "speed dial" on your telephone. You can program into your radio, one or more "buddy boat's" MMSI numbers and then use the DSC function to automatically contact your selected "buddy boat" and re-channel them to your current selected radio's channel. Your radio's instruction booklet will describe how to do this.

This feature is wonderful if you are in a location where many other cruisers are located and the "morning net" or whatever is used to try to contact your buddy. You bypass having to publically call your buddy boat. If your buddy boat's radio is not turned on, your radio will indicate that. On some radio's you can even make "group" DSC calls, to contact more than one other "buddy boat" at the same time.
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Old 15-03-2012, 08:34   #11
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Re: VHF with DSC - Mayday

Quote:
Originally Posted by osirissail View Post
Big NO, NO on the underlined & bolded part. Manually switching your radio to Ch 16 after you have initiated (pressed the DSC Distress button) a DSC distress call - will CANCEL your DSC distress call.
Wrong. After you send a DSC distress call, your radio will automatically switch to channel 16 but will continue to send the distress call on channel 70 (in the background) until it is acknowledged.

Quote:
But on all brands of radios, a DSC Distress call when activated will broadcast a distress command on Ch70 and then it waits for an acknowledgement from somebody's radio (which could be the USCG
Only the CG can acknowledge a DSC distress alert via DSC. Class D radio's cannot do this. If a boater continues to hear an unacknowledged distress call, they can contact the boater in distress via channel 16.

Quote:
Then all the receiving DSC radios will automatically re-channel to channel 16.
The CG has strongly recommended that this automatic channel switching feature be turned off as it can create an unsafe condition if you are actively using another channel at the time. All modern radio's are now required to have the ability to disable this feature.

Eric
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Old 15-03-2012, 08:43   #12
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Re: VHF with DSC - Mayday

Quote:
Originally Posted by fairbank56 View Post
Wrong. After you send a DSC distress call, your radio will automatically switch to channel 16 but will continue to send the distress call on channel 70 (in the background) until it is acknowledged.

Eric
Hmm... I understood it only switched to Ch 16 after acknowledgement
but I am not a DSC expect

Going to Ch 16 manually does inhibit the DSC call repeat function on the IC-M402
From the Icom manual:

Adistress call should be transmitted if, in the opinion of the
Master, the ship or a person is in distress and requires imme-
diate assistance.
•All keys, switches and controllers on the transceiver are functional.
NEVER USE THE DISTRESS CALLWHEN YOUR
SHIPIS NOT IN AN EMERGENCY. ADISTRESS
CALLCAN BE USED ONLYWHEN IMMEDIATE
¯Distress alert contains (default);
•Kinds of distress : Undesignated distress
•Position data : Latest GPS position data held for 23.5 hrs. or
until the power is turned OFF.
¯The distress call is repeated every 3.5–4.5 min., until re-
ceiving an ‘acknowledgement.’
¯Push [DISTRESS] to transmit a renewed distress call, if
desired.
¯Push [16] to cancel the ‘Call repeat’ mode.
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Old 15-03-2012, 09:15   #13
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Re: VHF with DSC - Mayday

The M402 is not a class D radio. It must remain on channel 70 to receive an acknowledgment. Just one of the reasons these "SC-101" radio's are now outlawed.

Eric
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Old 15-03-2012, 09:20   #14
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Re: VHF with DSC - Mayday

Here: Everything you need to know>>> Digital Selective Calling

&>> http://www.shinemicro.com/aboutmmsi.asp


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Old 15-03-2012, 09:25   #15
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Re: VHF with DSC - Mayday

Quote:
Originally Posted by fairbank56 View Post
The M402 is not a class D radio. It must remain on channel 70 to receive an acknowledgment. Just one of the reasons these "SC-101" radio's are now outlawed.

Eric
Thanks Eric, that makes sense.

BTW, when you use the term "outlawed", it this a figure of speech indicating that "SC-101" is no longer current / manufactured /sold OR that the use of these radios are illegal (in the USA)?

FWIW, Oz has no official shore based infrastructure that supports DSC - we are the poor cousins here!
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