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Old 20-10-2010, 16:45   #1
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DSC Calling for Other than Distress ?

We got our two Standard Horizon HX850S handheld VHF radios today. They may be an outdated model but fit our needs perfectly !

Reading the instructions reminded me of reading VHS video recorder instructions back in the 80s. While I'm a professional geek I wonder how many boaters actually bother reading the DSC instructions and therefore use the DSC features for anything but distress calls ? I can imagine a lot of radios out there with the VHF equivalent of the blinking 12:00 display on video tape decks.

So, do any of you use the DSC feature or is it a good idea that will probably fade away ?



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Old 20-10-2010, 17:07   #2
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One of the nice features of DSC is, if you know the other boats MMSI, to send private messages. In "monitored" waters, this can be a very nice feature. It can take a bit of time to program a message so Twitter/text experience is an asset.

  • Privately hail another DSC equipped vessel, or shore station, with a known MMSI number. Like having a "VHF phone number" this avoids having to monitor high traffic channels just for a hail from your boating buddy. It even "rings" your radio, similar to a telephone, notifying you that you have a call and then switches you automatically to the channel your caller is waiting on.

  • If properly connected to a Loran or GPS, a "Polling" feature transmits your vessel's position, in digital display, that can be monitored by DSC equipped home station/fleet station or boat.

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Old 20-10-2010, 17:14   #3
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I've been reviewing the spec on ICOM 802 SSB on and off for some time. Some of the issues are "how do you effectively test the thing?" and "don't you need two parties to have DSC to make it usable?" and "seems like a lot of menu fanagling to get to your message of choice etc"

Not sure the GPS is a function of just DSC but could be more inline to APRS

I'm not sure it's worth the money. Similar to ICOM and their D-LINK spec on HAM gear.

Ask yourself "Do I really need this with all the other technology I have?" especially if I am only using a VHF radio?
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Old 20-10-2010, 17:19   #4
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I know that the crews on the Naval Academy's new fleet of "Navy 44" sail training craft are using it for position polling on each other during training and/or racing events. Now that I'm installing class B AIS transponders on them though, they will not need to do this any longer although the DSC polling would get better range than AIS.

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Old 20-10-2010, 17:26   #5
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I'm confused on the range issue between DSC and AIS, if they are both using VHF? Is this not the case..or is DSC SSB?
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Old 21-10-2010, 01:20   #6
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AIS requires VHF (range is VHF limited)
DSC is available on VHF (range is VHF limited)
DSC is available on HF SSB (range is HF limited)
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Old 21-10-2010, 01:43   #7
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DSC radio use in the US and Caribbean is only in its infancy compared to Europe. My DSC VHF in the Caribbean only had a handful of DSC messages during the 6 month period that I had it on almost every day from sunrise to sunset. Compare that to the >10 messages per day that one would see in typical european locations or even higher amounts in busy areas such as the English Channel.
Particularly with bigger ships, combining AIS (to automatically get the MMSI and track information) and using the MMSI to directly and digitally hail the vessel sure beats a Ch. 16 call "Big boat about to run me over, do you see me?".
Using DSC on VHF or SSB for a distress message offers the distinct advantage that it automatically repeats until cancelled, potentially freeing the radio operator temporarily for other roles in an emergency.
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Old 21-10-2010, 03:15   #8
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Quote:
Originally Posted by SaltyMonkey View Post
I'm confused on the range issue between DSC and AIS, if they are both using VHF? Is this not the case..or is DSC SSB?
I was talking about class B AIS which transmits at 2w, while DSC is at 25w. Class A is a different story. There would be little difference in range between AIS at 12.5w and DSC at 25w.

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Old 21-10-2010, 04:30   #9
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SH can pickup the number right from the plotter (via the AIS data), so making a DSC call is simple. I think it also stores the incoming numbers so calling back should (?) be simple.

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Old 21-10-2010, 06:48   #10
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It amazes me that although DSC has been around for over 10 years, so few people use it for for private purposes - hopefully you never have to in an emergency.

Folks will spend hours trying to contact sailing buddies then have a lengthy voice exchange clogging up a channel for several minutes, just to establish each others position.

Although DSC on HF IMO is of very limited value for private use given the range of frequencies, modulation, propagation etc, on VHF where you have a limited range of channels, & know the range & capabilities it makes so much more sense.

Once you know your buddie(s) MMSI number you can program it in to your DSC VHF & have the following digitally controlled facilities to another DSC/VHF transceiver:

1) Call his/her radio with request to change to a channel of your choice in order that you can conduct a voice exchange. If the radio being called has auto ack enabled it will switch to this requested channel.

2) Poll his/her radio for their position - reply can be automated so within a couple of seconds you see their position displayed on your radio.

3) Send your position to him/her.

4) Answer any of above requests sent to you manually, or have your radio answer automatically if you have auto ack enabled. This is very useful at night time if you don't want the sleeping crew woken with the loud DSC squawk you get otherwise.

These are just the private functions, you can make Emergency, All Ships & Group calls as well.

If you have a VHF/DSC transceiver you have all these facilities available to you now. To set up is simple.

Connect your GPS to radio
Enable DSC watch
Enable auto ack (aknowledge) if you want to automate the replies to DSC calls as mentioned above.

How to do this obviously varies between models but it will be shown within the pages of the manual which you glossed over when first installing the radio

DSC range I have found to be slightly less than acceptable voice - say 28nm for DSC & 32nm for voice as a rough average over clear water for well set up radio's. This can vary enormously depending on terrain between boats though.

Hook it up, set it up then try it out - you will be amazed how easy it is.
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Old 21-10-2010, 07:06   #11
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We regularly use VHF DSC calls between the boat (Icom M601) and dinghy (SH HX850S). Very convenient and avoids having to listen to every transmission on a channel. I also have a group set up for cruising with friends.
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Old 21-10-2010, 07:22   #12
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Quote:
Originally Posted by richardhula View Post
It amazes me that although DSC has been around for over 10 years, so few people use it for for private purposes
Exactly, that was part of my reason for bringing up the question. Looking at the manual I thought maybe the instructions put users off, but maybe it is because you have to take the step of getting the MMSI number ?

I have never ever heard any chatter about DCS calling either over VHF or in person so there is definitely something holding up acceptance and use.



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Old 21-10-2010, 07:26   #13
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It sounds good. I have looked at the DSC chapter in my radio, but it sounds kinda complicated. When driving through a high traffics area it is faster for me to call each boat on 16 than to look down, scroll through the list of DSC numbers on the AIS, type one into the radio and press send and wait for response then select poll or send position. I have called the radio manufacturer and asked if there is an easier way, but they stated at this time automatic DSC calling of a selected AIS target is not possible as they are on different circuits. Maybe on the newer model? (In a non urgent situation like when I'm not trying to avoid a barge, another cruiser and two jet ski's jumping our wakes, while steering between two hidden and poorly marked shoals thats the only connection between the intercoastal and the shipping channel that may or not have a couple of huge freighters coming from a hidden corner), I might be more inclined to sit down and experiment. Outside the traffic I dont have anyone to call, most cruisers dont have AIS, and the barges aren't inclined to chat. Maybe if a couple of nearby cruisers were to publish their DSC numbers and book a time to anchor somewhere and practice??
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Old 21-10-2010, 07:26   #14
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Quote:
Originally Posted by SvenG View Post
Exactly, that was part of my reason for bringing up the question. Looking at the manual I thought maybe the instructions put users off, but maybe it is because you have to take the step of getting the MMSI number ?

I have never ever heard any chatter about DCS calling either over VHF or in person so there is definitely something holding up acceptance and use.

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Old 21-10-2010, 07:36   #15
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Originally Posted by Auspicious View Post
We regularly use VHF DSC calls between the boat (Icom M601) and dinghy (SH HX850S). Very convenient and avoids having to listen to every transmission on a channel. I also have a group set up for cruising with friends.
Do you have two MMSI numbers or do you use the same number for both sets when calling ?

Edit: just found this comment on Panbo
Quote:
It makes a wonderful dinghy radio; even with the same MMSI programmed into the HX-850 and my IC-M601 fixed VHF on the boat the DSC allows calling one another really straightforward.
That may break the strict interpretation of the rules about using the MMSI only on the boat/ship it is assigned to but I guess one could argue that the tender is part of the boat/ship. It sure would be convenient.




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