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Old 02-05-2015, 23:00   #1
Jd1
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M802 and DSC

When I first heard about DSC, I thought it was the neatest thing since sliced bread. The concept was very much like a telephone - you have your radio on and if somebody calls you it in effect 'rings' to tell you that someone wants to talk to you. In comes the default configuration of the M802. The way the radio comes from the factory, it gives a single, very short beep to let you know you have an incoming call. If one is sailing (no extra noise) without much wind and not doing much else then yes, chances are you hear the beep. What do people with motorboats do ? What if you have people talking or music playing? What if you are snoozing?
Maybe I don't fully appreciate the logic behind DSC? If it is supposed to work in a sort of phone like fashion then why the short beep? I have not found a method of changing the setup. Ideally I would like it to ring like a hone and keep ringing until I acknowledge the call.
Thoughts ? Comments ? Solutions ?
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Old 05-05-2015, 21:53   #2
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Re: M802 and DSC

Any comments at all ?
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Old 07-05-2015, 09:50   #3
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Re: M802 and DSC

Quote:
Originally Posted by Jd1 View Post
Any comments at all ?
Digital selective calling is like a paging system. It sends a notice, like a pager does, to a particular recipient.

The digital selective calling radio alerts its operator that it has received a page. The manner of the aural alert is specified. See:

http://www.itu.int/dms_pubrec/itu-r/...0-I!!PDF-E.pdf

The section of the document that seems most applicable is Section 12, Shipborne human machine interface (HMI)

See the subsection under the heading, "SHIPBORNE AURAL ALARM." The aural alarm is described as follows:

Quote:
12.1 Shipborne aural alarm

Shipborne alarms should start softly and increase in volume if not silenced by the operator. This will give the operator the opportunity to acknowledge the alarm without interrupting the ship’s current communications. It should be possible for the operator to disable all audible alarms except those of distress, priority and urgency.

Distress and urgency calls should have a distinctive two tone alarm. The alarm should consist of two substantially sinusoidal audio-frequency tones, transmitted alternately. One tone should have a frequency of [2,200] Hz and the other a frequency of [1,300] Hz. The duration of each tone should be 250 ms.

Distress calls and urgency calls should activate an alarm. For HF and MF distress calls, the alarm should activate only when a distress alert, distress acknowledgement, or a distress relay is received and the distress position is within 500 nm (926 km) of the receiving vessel’s position, or if the distress position is in the polar areas (latitude greater than 70 N or 70 S). The alarm should also activate when the call is received and the distance between the vessel in distress and the receiving vessel cannot be determined.

NOTE 1 – Disabling of aural alarm does not affect handling of call.

For geographic area calls, the alarm appropriate to the category should activate when the receiving station’s position is within the area specified by the call or the receiving station’s position is not known. The alarm should not be activated where duplicate distress relay calls are received within one hour. A duplicate distress relay call is one having format specifier all ships or geographic area that contains identical message information, as defined in 8.1 and an identical distress MMSI.
If you feel your digital selective calling device is not conforming to the specifications, contact the manufacturer. Perhaps you have an older device and it conforms to a different specification.

Note that the recommendations just say a device "should" operate this way.

The digital selective calling VHF Marine Band radio that I have operates as specified above. The radio I have is noted to be in compliance with the recommendation cited above. When my radio is paged, it rings like a telephone to alert me. My radio is a Standard-Horizon brand. It is my experience that radios made by Standard-Horizon tend to conform very closely and very strictly with the ITU specifications for digital selective calling features. Other brands, perhaps not so much.
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Old 07-05-2015, 13:06   #4
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Re: M802 and DSC

Thanks for posting the regulations. My radio is a new Icom M-802 .... but as you said, it seems to only be a recommendation. I was hoping somebody could make me aware of some setup or other in the radio to increase the amount of noise the radio makes.
BTW, I also have a Standard Horizon VHF and it does exactly as yours does - it gives a telephone like ring which is perfect.
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Old 07-05-2015, 15:35   #5
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Re: M802 and DSC

Try asking ICOM?


Our M-604s can adjust volume for the foghorn and for external speakers, but I don't see anything (quick review) about adjusting the DS notification tone/volume.


I know the DSC distress tone and the WX Alert tone will almost launch me off the bridge...


Does the beep volume respond to the main volume knob?


-Chris
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Old 08-05-2015, 14:25   #6
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Re: M802 and DSC

Jens,
DSC is cool....and it is one of the greatest advancements in maritime comms....(greatest thing since sliced bread?? not sure, but it is cool...)
BUT...
Quote:
Originally Posted by Jd1 View Post
When I first heard about DSC, I thought it was the neatest thing since sliced bread. The concept was very much like a telephone - you have your radio on and if somebody calls you it in effect 'rings' to tell you that someone wants to talk to you.
But, what you describe here is how most VHF-DSC gear works....not MF/HF-DSC gear....well, certainly not the M-802....now the Sailor 6350, now that's a great rig!!! (but, it will set you back about $10,000 - $12,000!!!)




You've gotten some good info here....maybe I can add some clarification???
Quote:
Originally Posted by Jd1 View Post
In comes the default configuration of the M802.....
Maybe I don't fully appreciate the logic behind DSC? If it is supposed to work in a sort of phone like fashion then why the short beep?
You're confusing the "DSC" system with individual radio design peculiarities....
And, as I wrote above, most VHF-DSC radios DO operate the way you desire....but many MF/HF-DSC radios are different....

I apologize to the purists for using some generalities here, but for ease of explanation / clarification Jens, here are a few points to remember, that will start to make things easier to understand...

MF/HF-DSC was implemented by the IMO under the SOLAS (Safety Of Life At Sea) conventions in 1992, as part of the GMDSS (Global Maritime Distress and Safety System), and although the "Distress" signaling part of the MF/HF-DSC system is alive and well, and is working quite well actually.....over the past 23+ years, some things have changed!

Ironically, the VHF-DSC system has GROWN in popularity and many VHF-DSC radios DO operate as you describe you wish the M-802 would....

Not the least of these changes over the past couple decades, is the rapid increase in use of satellite data communications for much of the business / shipping traffic, as well as much of the personal communications of crews (e-mails and SMS), and hence many of the intended "routine" uses of DSC signaling such as coast station-to-ship / ship-to-coast station, and ship-to-ship, traffic signaling, etc. never caught on, and hence there was little effort put into modern MF/HF-DSC radios in making them easy-to-use for this application, etc.
(although, if you listen to 12577 and 8414.5, most days you here quite a bit of DSC traffic, and only one-in-a-while is there a "distress" message....)

And, although the GMDSS was supposed to allow non-trained personnel (not the radio officer) to signal distress, etc. as well as use various communications gear, the fact is that it was still designed and spec'd out by radiomen / trained personnel.....so we ended up with a rather "technical" system after all...

Also, understand that the Icom M-802 is not a GMDSS-compliant radio....although it "technically" meets the GMDSS Class E requirements, it was never submitted for GMDSS compliance....and hence Icom could design it to meet the expected needs/desires of their market / make whatever changes they needed to make it less expensive and better suit the needs of their customers...



Now, throw all of those factors together....and you get what we have now....
An MF/HF-DSC system that works VERY well, but with very few pleasure craft using it!!
> 450 MF-DSC shore stations worldwide, and > 80 HF-DSC shore stations worldwide....and 100's and 100's of SOLAS vessels at sea daily....all of whom are monitoring MF/HF-DSC....and many of them DO use MF/HF-DSC, daily.....but again, few pleasure craft do...
{Is this a "chicken vs. the egg" argument??? not sure, but I don't think so....as with the reduction in both cost and complexity of sat comm gear, we have many pleasure craft sailors who opt for fried chicken nuggets instead! }



I know I haven't solved your issue....but at least I explained it pretty well...
And, I hope this does help...

Fair winds...

John
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Old 08-05-2015, 14:53   #7
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Re: M802 and DSC

Quote:
Originally Posted by ka4wja View Post
I know I haven't solved your issue....but at least I explained it pretty well...
And, I hope this does help...
John
Thanks ... it helps to have the background and it also helps to know that I can stop beating my head against the wall
I did send an email to Icom just in case ...
The frustrating thing is that this looks to me like a pure software change. I guess the number of 802's sold per year does not warrant the expenditure and since there is no competition anyhow, why bother. It's a shame though .....

Regards
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Old 08-05-2015, 15:37   #8
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Re: M802 and DSC

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Originally Posted by Jd1 View Post
I did send an email to Icom just in case ...
If you are dealing with Icom USA I would encourage you not to expect much from them. They have proven to be useless every time I have contacted them on a technical issue, even when I had all the testing data that was required. I wish Furuno took them over and sorted them out.
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Old 08-05-2015, 16:57   #9
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Re: M802 and DSC

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Originally Posted by svlamorocha View Post
If you are dealing with Icom USA I would encourage you not to expect much from them. They have proven to be useless every time I have contacted them on a technical issue, even when I had all the testing data that was required. I wish Furuno took them over and sorted them out.
Icom America came through for me after three failed attempts at getting the right version of CSM-802 software for a current radio from Icom Canada. Only after I presented them with the email from Icom America did they send me the right version (CSM-802 #11 ver 1.0)
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