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Author Topic:   DSC Position Request
6992WHALER posted 11-08-2011 10:49 PM ET (US)   Profile for 6992WHALER   Send Email to 6992WHALER  
If two boats are equipped with DSC radios connected to GPS one boat can send a DSC position request to the second boat and the radio on the second boat will send back the position of the that boat to the first boat.

To test this I used the following boats:

The Holly Marie, a 23 foot Walkaround with a Garmin 3206 GPS and Standard Horizon Matrix GX2100.

The Emmarie Jean is a 16' 7" Sakonnet with a Garmin 172C GPS and a Standard Horizon Eclipse GX1000S.

Both boats have a MMSI number and both boats have the other boat's MMSI number imputed in their radios.
Both radios have been set to automatically reply to position requests.

The Holly Marie is going to request the position of the Emmarie Jean.

1: From the normal display on the GX2100 push the CALL MENU Button to go to the DSC menu.

2: On the DSC Menu, rotate the channel knob to select position request. Push the select soft key.

3: On the position request call list menu, rotate the channel knob to select the name of the boat to call. Push the Select soft key.

4: Push the yes soft key on the display to transmit a position request to the Emmarie Jean

5: The position of the Emmarie Jean is now displayed on the Holly Marie's GPS. Bearing 276M 19.6 ft away.

6: Looking to port from the Holly Marie we see the Emmarie Jean about 20 feet away.

jimh posted 11-09-2011 09:00 AM ET (US)     Profile for jimh  Send Email to jimh     
John--Thank you for the very interesting narrative and pictures of your DSC position poll experiment. I think you have reached the same conclusion that I have:

In order for a boater to test his DSC radio he has to own another DSC radio himself to test with.

This comes about because, as the USCG noted, about 90-percent of the DSC radios installed in recreational boats are not properly interfaced to their GPS receiver. I suspect that an even higher percentage, more than 90-percent, are not interfaced to a chart plotter. So the chances of randomly finding another boat with a DSC radio that can do a position poll test is probably about one in one-hundred.

K Albus posted 11-09-2011 09:16 AM ET (US)     Profile for K Albus  Send Email to K Albus     
I noticed in John's pictures that the only other boat saved in his list of MMSI numbers was "ConWave", which I presume is ContinuousWave.

On my new boat I have the VHF radio and the GPS chartplotter interconnected, and I have received and programmed my MMSI number into the radio. I'm now a part of the 10%, and I will be happy to run a test with you in the spring, Jim.

jimh posted 11-09-2011 10:25 AM ET (US)     Profile for jimh  Send Email to jimh     
Kevin--I look forward to including you in the coterie of vessels whose MMSI is in my radio's call directory, but you first have to tell us the name of your vessel. (And, then, or course, its MMSI.)
6992WHALER posted 11-09-2011 10:45 AM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
Kevin you are correct, ConWav is ContinousWave. (the only DSC equipped boat I know)

Unfortunately when Jim and I have run together I did not have my GPS connected to my DSC radio. We have used the DSC call feature to call each other but with my installation incomplete we could not use the position options.

A great example of the potential of DSC and GPS is when we left Killarny this summer on that foggy rainy morning.

As we motored off, Jim had a problem at the dock and did not leave as scheduled.
He could not talk to me as I had changed my radio to a weather channel. His solution was to use a DSC call. My radio immediately alerted me to Jim's call and automatically changed my radio to the channel Jim was on. After talking we decided that the three boats that were already underway would continue at a slow pace until Jim resolved his problem and caught up. This would have been a perfect time to use the position request features. We would have known the exact location of both boats. With the wave and weather conditions as they were visibility was poor, I only saw Jim when he appeared on my radar about 1 mile away. I was not too concerned about him missing us, as the channel was fairly narrow, but the knowledge of his exact location would have been reassuring.

Kevin- I hope I also get a chance to use the DSC technology with you next summer.

David Pendleton posted 11-09-2011 11:43 AM ET (US)     Profile for David Pendleton  Send Email to David Pendleton     
My radio (a Raymarine Ray 55) pretty-much forces you to interface it with a GPS. If you don't do this or input a position manually, it will beep like hell until you do.

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