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Old 14 April 2012, 23:09   #61
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As copinsay has said above in this day and age of DSC fixed or handheld equipment being fairly cheap ( well in the grand scheme of the maritime world anyway) and the advantage it brings it would be a bit silly not to at least consider it. Certainly many larger commercial vessels no longer listen to Channel 16 relying on DSC to alert them.

A few things to remember though. If you buy second hand in will need to be " reset" by either a service centre or the manufacturer to allow your MMSI number to be input. You will also need to update your ships radio licence with ofcom to get an MMSI number. If you haven't done a radio course recently ( by that I mean since DSC was included) then I would strongly recommend it. Trust me 1 days learning and getting it right can save your life especially if you sink quickly and all you get out is the DSC ( and on that subject it helps if you send a Designated distress using the menu that comes up when you first press the red button rather than undesignated where you just press it then press and hold). Finally make sure you show all your crew how to contact the coastguard in an emergency and what to say. There is nothing worse that the only person who knows going overboard and the person who calls for help not knowing what to do.

On the subject of distance it depends on the weather or more specifically the atmospheric pressure. In high pressure from Solent coastguard we often get cross Etal in the south of France, stavanger in Norway and have been known to get good 2 way comms with our colleagues in Shetland! As said though boat to boat for 2 Ribs it will be limited by the height.
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Old 15 April 2012, 02:13   #62
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after reading all this input,albeit some on the light side, and some very confusing i will in no doubt be getting adsc unit when i can, i do need to do the license thing so it will be on top of the adgenda for things to do and get,menwhile tho i will have to persevere with what i have or havnt got and stick inshore! as i have already said i wont be going out in bad weather and i carry life jackets, and saftey equipment etc, so for now i will be able to manage with what i can get
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Old 16 April 2012, 07:19   #63
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Just an observation, but if all radios auto- relayed every DSC Discress call, I'd be bobbing around off Oban calculating how long it would take to get to the solent to help the stranded yacht after the dstress call is relayed round the coast....... 5 weeks later one of our Auzzie mates rocks up in his rib to help.....


Smiffy,

I may be wrong, but I doubt you could even buy a non DSC radio new these days (happy to be corrected on that). Having the kit is one thing, knowing how to drive it properly is another.

Get yourself on a course - then you will find out for sure what it's all about. Bottom line is a DSC distress call is of limited use if the recieving boat has no way of plotting that lat / long on a GPS of some description (hence my chinagraph pencil comments above), or has an old radio that don't talk digital.

A DSC "red button" should always be followed up by a vox call.
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Old 16 April 2012, 08:20   #64
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9D280. They don't ever auto relay even the big ship kit. But the class D equipment most leisure users have has the ability to "relay" removed. It would be just the same principle for DSC as for voice in doing a mayday relay to a coastguard station if they did not hear the distress vessel.

I couldn't agree more on the getting training and as you have said DSC is just an "alerting" medium. It does not replace the voice broadcast which should always follow the DSC. Also it seems to have become common practice but I always say give BOTH a lat and long position and if you can a range and bearing from a prominent point. It makes life a lot easier for Both the Coastguards and the listening stations.
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Old 16 April 2012, 11:19   #65
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I was asked this question at the weekend:

You are out on the RIB in the Solent, your engine catches fire and you need urgent assistance. What do you do first? You have a VHF with DSC on board.

Suggestions?
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Old 16 April 2012, 11:40   #66
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Depends on the severity of the fire, but...

1) Punch DSC emergency,

2) fight fire as capable, else:

2A) voice mayday call, else:

3) Abandon vessel

Primary goal: Stay alive, 2nd goal: Summon assistance/rescue, 3rd goal: limit damage/extinguish fire.

Least, that's my take on it.

jky
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Old 16 April 2012, 12:05   #67
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Quote:
Originally Posted by al_typeR View Post
9D280. They don't ever auto relay even the big ship kit. But the class D equipment most leisure users have has the ability to "relay" removed. It would be just the same principle for DSC as for voice in doing a mayday relay to a coastguard station if they did not hear the distress vessel.
That was my point. If all the DSC VHFs "auto relayed, within minutes bods in Oz would be getting the distress signals form the Irish sea, and by the laws of timing & lag, the system would very quickly saturate as the "echoes" start doing laps of the planet and radios get the distress signal ralayed back to them....

Quote:
Originally Posted by jyasaki View Post
2) fight fire as capable, else:
I have been thinking about tackling engine fires, but will put my thoughts in thre "engines" section so as not to hyjack this thread.

Quote:
Originally Posted by jyasaki View Post
Primary goal: Stay alive, 2nd goal: Summon assistance/rescue, 3rd goal: limit damage/extinguish fire.
Agreed, although I suspect you may have just started a "fight fire" vs "shout help" and which will be more effective at keeping you alive debate....
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Old 16 April 2012, 12:12   #68
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Here is a nice antenna test. Seems they are getting about 14 nm from their radios with an 8 foot antenna. I went with the Shakespeare 5225 XP after reading many reviews. I don't expect nearly that range except to the Coast Guard since mine is mounted at water line just about.

http://www.llelectronics.com/docs/aw...HFAntennas.pdf

DSC travels WAAAY further than voice. Below is a test run with a Nautilus Lifeline VHF which is made for scuba divers, since it can be submersed to 300 ft.

My personal unit.


Hi, Mike Lever here, President of Nautilus Lifeline
here is a comprehensive range test for all who are interested.
safe diving!!

June 29th 2011
Lifeline position report test


Radio : WestMarine VHF580 DSC Marine radio
Radio Tx Info
modulation +- 5 khz deviation
Frequency range : 156 to 158 Mhz
Frequency stabilty +- ppm@ -20 to +50 Celsius


Radio Receiver info
Frequency: range 156 to 163 Mhz
Sensitivity: 0.25uV for 12 dB SINAD
Circuit : Duel Conversion super heterodyne PLL (Crystal for DSC)
Squelch Sensitivity: 0.2 uV threshold
Spurious response: 75 dB
Adjacent Channel Selectivity 78dB @ +- 25KHz
IF Feq: 1at 41.925 Mhz 2nd 455 kHz
If Feq DSC : 1st 21.7 KHz 2nd 455 kHz


Atenna : Galaxy Antenna 5108
Shakespeare Galaxy Eliminator Series found on page 194 of the western marine catalog
SHA-5018-FLT , 17.5 feet long gain 9db


mounted to the mast using the standard Shakespeare mounting kit
found on page 201 western marine part Number : SHA 410


The Antenna is mounted on the Stbd side of the aluminum mast about 2 feet off set from the mast with the antenna whip clear above the top portion of the mast


DSC position report tests
Unit # 024 and 025
Version info
HW:0:01 SW:0.37
software 0.3.14
region : 4
Single position report only


LL was tested by Tim Courtier
tester held radio at all times during testing while lying on dive deck of the skiff holding the LL over on on the water , Line of sight held between LL and swell at all times


WX
Vis:2nm
light rain
2'chop SE


SWELL LOC : 56 45.389 N
132 35.523 W


Line lines tested at different heights above the water once a fail RX was reported for the position report by the swell
LL tested -0.5 - 4 inches from water


Time16:56
Dist 1.8 nm
56.46.420N
132 38.437 W
DSC OK TX
VOICE OK TX


Time 1700
Dist 2.6 nm
56.46.751N
132 38.672 W
DSC OK TX
VOICE OK TX


Time: 1704
Dist 3.5 miles
56.47.141N
132 41.078 W
DSC OK TX
VOICE OK TX


Time: 1708
Dist 4.3 miles
56.47.547N
132 42.452 W
DSC OK TX
VOICE OK TX


LL Tested at 12 inches above water after a single fail while 4 inches from water


Time: 1709
Dist 5.3 miles
56.48.046N
132 43.886 W


DSC OK TX
VOICE Broken but readable


Time: 1712
Dist ? miles
56.48.000N
132 43.000 W


DSC Rx ok on swell - tho eroneous data ?? ...
location is not fully formed


Time 1719
Dist 6.1 miles
56.48.555N
132 45.170 W
DSC OK TX
VOICE very broken up


Time 1722
Dist aprox 7 miles
56.48.576N
132 45.244 W
DSC was transmitted from at lest 7nm from the swell
tho the GPS reading only shows a movement of 200 yards from the last position
thinking this is from the LL losing Gps while bouncing around my seat in the skiff , then me pressing TX before it relocates ..
i also found this to happen during some testing earlier this day, LL was tested on the nautilus , i closed it ,
and left with the skiff , 5 min later i popped it open and pressed send without waiting for the sat lock . it worked from 2nm from the swell but showed the swells location as the pos report


Time 1727
Dist 7nm miles
56.48.876N
132 46.590 W
DSC OK TX
-------------


LL held 18 inches above water or so . i measured from my finger tips touching the water to my elbow and used that as the height a diver would be holding it up and out of the water


Time 1730
Dist 7.8 miles
56.49.073N
132 48.136 W
DSC OK TX


Time 1734
Dist 8.6 miles
56.49.202N
132 49.785 W
DSC OK TX


Time 1740
Dist 9.5 miles
56.49.313N
132 51.375 W
DSC OK TX


Time 1734
Dist 11.8 miles
56.49.582N
132 55.428 W
DSC OK TX


11.8 NM tested both radios , distance was confirmed by a navigation buoy and nautical chart
radios tested about 6 times at this location all DSC position reports received by the Nautilus when the LL was held Apox 22-23 inches from water
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Old 16 April 2012, 13:44   #69
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My thoughts were to put out a verbal mayday first before doing the DSC, on the basis that it only takes seconds to yell for help and then do the DSC which may take longer fiddling about trying to remember exactly what to do. I have 2 GPS's that constantly display Lat /Long, so that info is easily to hand. I am also assuming that if there is a boat nearby, they hopefully will react to a verbal Mayday and head to me asap, whereas there are so many false alarms on the DSC, where it has been set off unintentionally, that people intend to get pissed off with it and all they do is reset it, possibly without bothering to check the details. It is a difficult one to call. Either way I will be trying to atract attention as quickly as possible. To reduce the risk, I have a master cut off switch for the batteries on my consol that means I can kill the electrics to reduce the risk of an electrical fire. The only items not turned off by that are the GPS's and the radio.
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Old 16 April 2012, 14:32   #70
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Quote:
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My thoughts were to put out a verbal mayday first before doing the DSC, on the basis that it only takes seconds to yell for help and then do the DSC which may take longer fiddling about trying to remember exactly what to do.
Lift cover, push red button. You get out the distress call, your vessel ID (vis MMSI), and, if connected (and working) GPS location. See how long it takes to transfer any single piece of that info via VOX.



Quote:
I am also assuming that if there is a boat nearby, they hopefully will react to a verbal Mayday and head to me asap,
Dunno. Unless boaters there are much more attentive and prepared than here (where I've seen vessels two hundred yards off ignore an assistance call), I'd rather shoot out the canned message to people who are actually [supposed to be] listening, and get on with dealing with the problem.

Any DSC-equipped boat will likely do what you said. Any other may or may not, especially when you consider the one shot they have at your lat/long is as you speak it (DSC you should be able to scroll the positional info back.)

As I said, it depends on conditions: What is at risk from the fire, how much time you've got, etc.

Quote:
whereas there are so many false alarms on the DSC, where it has been set off unintentionally, that people intend to get pissed off with it and all they do is reset it, possibly without bothering to check the details.
Really? I've only heard of two here in the past, oh, three years or so; one was an unregistered unit (no MMSI info, no position, thus no resolution; don't know if the CG did a DF to locate), and one was a child playing with the mic on a docked boat (oops.) Maybe not representative, as one had no position data to respond to, and the other had a position within the harbor.


Quote:
It is a difficult one to call.
It is, primarily due to the many variables that will come into play that may affect the response pattern. Having a plan is important, but knowing that you may need to deviate from the plan if required is just as important.

jky
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