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Author Topic:   Two DSC Radios on Boat
DeeVee posted 01-20-2013 11:32 AM ET (US)   Profile for DeeVee   Send Email to DeeVee  
I recently acquired a Standard Horizon GX1700, DSC capable VHF radio to add to the electronics array on my 1989 Outrage 22. This radio includes an integral GPS receiver. The original DSC capable VHF that was installed on the boat when I acquired it, a Standard Horizon GX2355S, remains on the boat, connected to my Standard Horizon CP175CF GPS chart plotter.

The equipment, though dated, and somewhat obsolete, seems to be operating fine. During the past fishing season, the radio would lose position data occasionally, probably due to an intermittant connecton with the GPS. I believe I have corrected this condition during the relocation the GPS antenna required by the new VHF anntena installaition. I feel I have two reliable, independent, DSC capable systems on the boat. One modern, class D, up to date system and one dated, though operational system.

I have not programmed the MMSI number into the new system as of yet due to a question I have concerning protocol for two DSC radios on the same boat. One of the FAQ subjects asked specifically if the same MMSI number can be programmed into two radios on the same boat. The answer was yes, two radios on the same boat can have the same MMSI number.

Is there a scenario where one may want two MMSI numbers on the same boat? I could not think of a reason. The new radio only allows one chance at programming the MMSI number (it would have to be sent to a factory service provider to clear the program if it is programmed incorrectly), I would like to hear another point of view concerning the subject.

Thank you,
Doug Vazquez

jimh posted 01-20-2013 12:42 PM ET (US)     Profile for jimh  Send Email to jimh     
I cannot speak authoritatively on this topic, but I will comment that my boat is very likely going to have two radios with different marine mobile service identities (MMSI). This is because I have already coded one radio with an MMSI that was issued by BoatUS from their MMSI program. Since then, I have obtained another MMSI, this time from the Federal Communication Commission (FCC). The FCC-issued MMSI is an identity that is registered into the international database of MMSI registrations, so it can be useful in foreign water. Since I do a lot of boating in foreign water--Canada--I thought it best to be compliant will all the regulations that apply to radios. That prompted me to get a ship station license for my radio. The MMSI was not an added cost, so I asked for one, too.

I am almost at the same point of decision as Doug, except that I have not purchased the new radio. I am waiting to see what new products come out this Spring. When I do get the new radio, I will program the new radio with the FCC-issued MMSI. Then I will have two radios on the same boat with different identifiers. If nothing else, I suppose I can call myself from one radio to the other. I think that you can even do that with two radios with the same MMSI, but I have not verified it.

To speak directly to your situation, Doug, I would suggest that you use your present MMSI on both radios, unless you have some plans to change the MMSI, for example, by getting an FCC-issued MMSI. I would not register the same boat twice into the BoatUS MMSI system. That does not seem like it holds any advantage.

The fundamental problem with the MMSI decision on radio encoding is the one-time-only programming. This is a provision of the ITU recommendations which has been made into regulation by the FCC. I believe that all the currently-sold fixed-mount radios in the USA will be DSC Class-D radios and will be compliant with the regulations, so you will only get one chance as the end user of the radio to program the MMSI. If you need the MMSI changed, you will have to send the radio back to the manufacturer, which will likely incur some costs.

DeeVee posted 01-20-2013 01:49 PM ET (US)     Profile for DeeVee  Send Email to DeeVee     

Thanks for the thoughts. Though the state of Washington is adjacent to Canada, I have not entered any Canadian waters since I bought this boat (7 years ago), though I am sure I have been very close to the border of British Columbia in the Strait of Juan de Fuca.

I think I will keep it simple and program the same MMSI number into the second radio.

Speaking of the second radio, I was at first concerned about how well the GPS receiver would receive satellite signals, housed below my t-top canvas, within the overhead electronics box.

Before I finalized the mounting location, I placed the radio in the electronics box, connected the existing VHF antenna (just in case I keyed the microphone by accident) and turned on the radio.

Though the boat is stored under an open, wood framed, composition shingled roof, the internal GPS receiver was able to obtain a 3D position fix, with good signals from several satellites. I did not record how many satellites, but I believe 7 satellites were able to be received.

I believe the radio's GPS receiver will perform adequately on open water, even located within the electronics box, below the canvas top.

The only feature that I believe I will miss on this radio, is the lack of a speaker in the microphone. My old radio has this feature and I found myself using the speaker in the microphone quite often, by holding it close to my ear while under way, between my transmissions. We'll see how well I can hear the new radio in the same situation. I suppose I could buy the optional "RAM" microphone offered by Standard Horizon to overcome this problem. Or simply use the old radio.

Thanks again,
Doug Vazquez

6992WHALER posted 01-20-2013 07:47 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
I installed a Standard Horizon Explorer GX1700 last spring. The radio is my second radio or redundant DSC radio. I am going to program it with a new MMSI number. Like Jim I am going to get an FCC issued one.

The second reason I installed the second radio was to allow me when I am traveling with a second boat to keep one radio on 16 and the second radio on a working channel to communicate with my fellow traveler. If I install the same MMSI number on both radios every time I receive a DSC call both radios will respond and change to the same working channel. If I have two MMSI numbers only one radio will respond to the call leaving the second radio on 16.

My GX1700 radio is mounted in my dash under my hard top. The unit has never had any trouble finding satellites. I also miss the speaker in the microphone. If it had an anchor drag alarm this radio would be perfect for me. Even with out it I will say that I am very happy with the Standard Horizon GX1700 radio as a standard VHF radio and a GPS receiver. Without a MMSI number I have not used its DSC features yet.

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