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Author Topic:   DSC Radio Trasmitting Distances
6992WHALER posted 02-10-2012 04:17 PM ET (US)   Profile for 6992WHALER   Send Email to 6992WHALER  
I recently attended a seminar on DSC radios. The instructor had a pelican case with two DSC Icom VHF radios and a Garmin 3206 Chart plotter mounted in it. The case is set up so you can see first hand how DCS radios operate. They have done something to limit the transmitting power so the demo does not activate near by DSC radios.

The instructor told us that he was not going to sent a distress call because he had not had time to talk to the local Coast Guard. According to him, the first time he used the unit, shortly after he did the DSC distress call demo, an employee of the hotel were he was teaching came and told him the Coast Guard had called and was trying to figure out why a distress call was coming from the hotel.

The man who set up the units was on the West coast. He received a call from the Coast Guard asking him about the DCS distress call they had received on the east coast. When he set up the radios he registered the MSSI number using his name with his information and saying it was for demonstration purposes only.

No boats in the nearby marina had their DSC radios activated.

The Coast Guard's receivers are so sensitive that they are saying (according to the instructor)that they are routinely receiving DSC calls 50 miles out. Even handheld radios are reaching out much further than the 20 mile range.

This makes me think a hand held radio with DSC and a built in GPS receiver is a more valuable/usable tool then a EPIRB or a Personal Locator Beacon for the type of boating I do. More bang for my buck. I hopefully will never use a EPIRB or a PLB but I know I will use a handheld VHF radio.

Hoosier posted 02-10-2012 10:18 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Maybe, but don't bet your butt on it. The DSC coverage in the northern Great Lakes is spotty. The Canadians have much better coverage in Superior and the North Channel than Rescue 21 does. As a matter of fact, according to the published USCG VHF radio coverage charts, they don't have ANY coverage around Isle Royale, but the Canadians have overlapping arcs out of Thunder Bay. At today's prices you can get a good PLB for around $200, that's a no brainer.
6992WHALER posted 02-10-2012 11:39 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
ya but if I boat with you I get to use yours for free.
jimh posted 02-10-2012 11:47 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't know if the USCG has published updated radio coverage charts for the RESCUE 21 system. The last time I looked the coverage charts were from the existing prior system. The coverage shown was based on reception from a 1-watt transmitter at 1-foot above the water. Any demonstration DISTRESS signals ought to be sent into a dummy load, not an antenna.
Hoosier posted 02-11-2012 07:09 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
I found this in an article from a Google search:

"On the East coast from Maine to the Florida Keys, on the Gulf coast all the way through to Corpus Christi, and on the West coast from San Diego to Seattle, you are covered. If you’re a Great Lakes sailor, you’re also covered along the eastern shore of the state of Michigan, and by the end of this year you should be fully covered on lakes Michigan and Erie as well. By next year coverage may also be extended to the Ohio and Mississippi rivers."

Notice that there's no mention of Lake Superior...

http://preview.sailmagazine.com/cruising/rescue_21/

Hoosier posted 02-11-2012 07:32 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Jim linked to this in last year's thread about this

http://www.uscg.mil/acquisition/rescue21/images/R21nationwide.jpg

There's no coverage at or around Isle Royale.

This begs a question about integration with whatever system the Canadians are using for DSC. I bring this question up because as of right now there is no integration of weather radar coverage between the US NWS and Environment Canada. I asked about it and got these replies:

From Canada

"Unfortunately we can only show Canadian content on our web site as we are a Government of Canada web site. The same is true in the United States with the products shown on their National Weather Service web site. However, private companies (Intellicast and AccuWeather in the US or The Weather Network in Canada) do not have to follow the same guiding policies."

From NWS

You are absolutely right...and I really wish we could, along with everyone else in our office. But that is way out of our control...way up the chain of command. It would, literally, take an international agreement between the two governments.
I wish I had better news or could be of more assistance...but rest assured that we share your frustration.

jimh posted 02-11-2012 12:17 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't think the ability of the USCG radio watch to receive these demonstration DSC DISTRESS calls is related to the receiver sensitivity. Just about all VHF Marine Band receivers have excellent sensitivity. The USCG radio watch is distinguished from other on-board receivers by the very tall and very nicely sited antennas connected to their receivers. It is the antenna location and antenna height that permits USCG radio watch stations to receive well, more so than their receiver sensitivity.
jimh posted 02-11-2012 12:52 PM ET (US)     Profile for jimh  Send Email to jimh     
Isle Royale National Park (IRNP) would be a great site to install a RESCUE 21 shore station, but I don't think a station there is planned. The next time a participant in this discussion is boating around IRNP, a test call should be made to the USCG to establish if they are able to effectively receive transmissions from typical recreational boats in that vicinity.
6992WHALER posted 02-11-2012 05:05 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
I am definitely not an expert on radio communication I might be miss quoting. Maybe I should have said equipment instead of receiver.
But either way I am impressed with what this instructor said the range of the system is.

If it is going 50 miles that covers a lot of water.

Also if I use a DSC distress call, any DCS equipped boat in range will know I am in trouble and my location. If I use an EPIRB or a PLB, I am limiting who will know I am in trouble.

David Pendleton posted 02-11-2012 06:33 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
I prefer not to rely on any one technology so I have all three.

75% of the time I spend on L. Superior, I am alone. I made all six runs to and from I. Royale alone.

I invested in the EPIRB first, then the PLB when they dropped in price. Both are really just so they'll find my body.

6992WHALER posted 02-11-2012 06:49 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
Dave, redundancy is good, but I think when you were up there fall 2010 the US Coast Guard station had already shut down for the season. So it would have taken a long time for the Coast Guard at the next open station to get to you. However if you had hit your DSC distress button, both CONTINUOUSWAVE and HOLLY MARIE would have responded. At 50 mph I could be there fast. I might have a concussion from the ride but I bet you would be buying me a beer (and a tank of gas) that evening.
jimh posted 02-12-2012 11:10 AM ET (US)     Profile for jimh  Send Email to jimh     
Dave--John's boat would arrive first. I would hang back to get some pictures of the rescue so I could write a good story about it.

If boating alone, one needs to approach some emergency situations with a bit more planning. I am very seldom alone on the boat, but when I am I tend to alter my methods. For example, I wear a PFD and attach the safety lanyard.

David Pendleton posted 02-12-2012 06:10 PM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
As you may recall, I have a wireless lanyard and self-inflating PFD. I also have a safety harness that works in conjunction with the PFD, but I've never used it.

One other point, as we have discussed here and elsewhere, most DSC radios are not programmed (with an MMSI) and not connected to a GPS. I think it's safe to assume that fewer-still are connected to a GPS and a chart-plotter.

I would fall into this category. My radio is connected to my GPS and I have an MMSI, but my chart-plotter does not support position requests.

If I were to receive a distress signal, and I were unable to make radio contact with the vessel in distress, I would have to plot the position manually. While I know how to do this, I don't do it very often. My personal response time to a distress call would be quite a bit longer because of this.

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