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btrayfors · 01-07-2010, 07:34

IMO, this thread -- with the excellent and factual contributions by John and Eric -- is a pretty good demonstration of why Osiris is right on one point: who needs MF/HF-DSC?

Most of the sailors I know really don't need it. Or want it. Why?

1. It's FAR TOO COMPLICATED for most sailors who are not professional or semi-professional communicators and tinkerers;

2. The Icom 802 manual contains 30 pages of description of DSC and it's various modes and uses. Who in god's name is gonna digest that -- or remember any of it -- when they're knee-deep in water?

3. It's very distracting. What is the use of knowing that someone in the Mediterranean is in distress when you're sitting in, e.g., Florida?

4. There are other alternatives, and better ones. Contrary to Osiris' dismissal of HF radio, it can be and demonstrably has repeatedly been an excellent way to advertise a distress situation, and to obtain help. There are hundreds of examples, and those of us who follow the ham maritime nets have heard many of them. Also, an EPIRB is used to SUMMON HELP immediately. You might be in distress and not need that, e.g., a sick or injured crew member who needs medical advice, or an emergency watch if you have a broken rudder or engine or whatever and are effecting repairs.

IMHO, your first priority is to sail the boat, using onboard navigational devices and the Mark One eyeball. It's not to spend your time mastering complicated communications systems which are nice, cutesy, sometimes finiky, often misunderstood, etc. and are decidedly marginal to your needs.

On the other hand, if you love technology and love to play with radios and think that somewhere, sometime HF-DSC might come in really handy, by all means go for it.

Bill

fairbank56 · 01-07-2010, 10:27

I agree with you Bill except for a couple points. If you have an 802 and it's properly connected to your GPS and you have an MMSI programmed and your out of VHF range and you have a dire emergency (sinking, fire...etc) you don't have to know anything about that radio other than to turn it on and press/hold the red button for 5 seconds. You can walk away and do whatever else you have available to get help. Also, anyone who receives the distress alert and doesn't hear a response from the Coast Guard or anyone else, should try to relay the message. You may very well be able to help that person in the Med by relaying to the authorities. If you find that distracting, then don't hook up your DSC antenna. You can still send your own distress alert if need be to get help and can still use the other non distress related DSC functions via your normal antenna.

Eric

fairbank56 · 03-07-2010, 05:41

Quote:

Originally Posted by Seahunter

Eric, when the AK comes in the 802 responds in kind, that's how they know.

As further verification of my bench test showing that the 802 does not "respond in kind" to receipt of an ACK from the coast station:

From ITU-R M.541-9 Operational prodedures for the use of digital selective-calling equipment in the maritime mobile service

2.2.8

If an acknowledgement is received further transmission of the call sequence should not take place. On receipt of an acknowledgement which indicates ability to comply, the DSC procedures are complete and both coast station and ship station should communicate on the working frequencies agreed with no further exchange of DSC calls.

Eric

osirissail · 03-07-2010, 06:22

Actually I have two HF radios and two antennas. One is the Icom M802 - without the DSC activated by installing an antenna for it. HF Radios are, IMHO, a vital safety feature on a cruising boat for weather, cruiser nets, and long range email/data services. In the boat/cruiser nets arena communication with other boats in your "flotilla" - say in the Pacific, or ARC or TransARC - gives you access to vital and valuable advise and assistance for less than "MAYDAY" situations. But HF radios are rarely, if ever, left "on" 24/7 or longer so as a "MAYDAY" device it is very low on the priority list. And salt water and the ocean atmosphere is very hard on HF equipment, cables, and antennas. Solar activity and a host of other complications make HF transmissions extremely variable from mere miles to worldwide. So as a "reliable" or useful "threat to life" communications system it is not viable any more than having the ability to utilize Morse code is useful.
- - VHF DSC is enormously valuable both for everyday "non-net" calls to/from friends and as a safety device since its 24/7 use underway is normal.
- - For "MAYDAY" situations (or potentially imminent "threat to life" situations) out of range of VHF, the EPIRB is the only viable, sure answer to getting assistance. The only action necessary is to pull the cord or with some models, water immersion will take care of your distress call while you are dealing with the immediate problem of keeping yourself and crew alive.
- - Use that money needed to buy/install the second HF antenna to purchase an EPIRB.

fairbank56 · 03-07-2010, 17:10

Quote:

Originally Posted by osirissail

But HF radios are rarely, if ever, left "on" 24/7 or longer

Probably true for non-commercial vessels, but there are plenty of commercial vessels on the high seas that do have them on 24/7 monitoring the DSC emergency channels as they are required to do and there are many coast stations monitoring 24/7 as well.

According to the Coast Guard the vast majority of DSC distress alerts are from MF/HF. Most of them are false alerts and relays. They were so overwhelmed with distress and distress relay calls that they put out notices to try to educate everyone on the proper procedures when using MF/HF DSC. This has helped significantly with the problem. Many of the alerts were true distress calls and with so many stations monitoring these channels, the system has proven to be very effective.

It only takes about 10 seconds to turn the 802 on and press the distress button. To write it off as an unviable method of summoning for help is very poor advice in my opinion.

By the way, for those of us that use it, and there are plenty of us, morse code is more effective under marginal propagation conditions than voice. I use it every day and have no problem making contacts at just about any time of day or night.

Nothing is a sure thing including an EPIRB. At least with HF, if you establish voice comms, you know help is on the way. With just an EPIRB, you have no clue whether it's working or not until help arrives on scene. I'm not knocking EPIRB's. Everyone going out of VHF range should have one. Every distress situation is different. If you have time to try to establish voice comms after your DSC alert, then do so. If you don't, then just send the DSC alert and launch your EPIRB. If you don't even have time to turn the radio on and send the alert, then just launch the EPIRB but don't just forget about the HF just because it "might" not work for you. Odds are that it will work just fine.

Eric