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Multiple VHF's single MMSI Question
03-23-17, 06:51 AM
Post: #1
Multiple VHF's single MMSI Question
If I assign the same MMSI number to portable radios with DSC e.g. Standard Horizon HX870. Will my my MDF e7 display each of the MMSI? Will I be able to communicate directly with them even though they share the same MMSI as the ship's MMSI? Will we be able to located the the DSC target? What if any problems are there vis-a-vie the MDF when having multiple portable units sharing the same MMSI as the ships MMSI... Thanks... Jon
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03-23-17, 10:57 AM (This post was last modified: 04-04-17 01:59 PM by Chuck - Raymarine - Moderator.)
Post: #2
RE: Multiple VHF's single MMSI Question
Welcome to the Raymarine Forum Jon,

General comment: The system is not designed to function in the manner which you have described. Should all VHF radios share the same MMSI and be configured to automatically respond to position polling requests, then all will respond. Typically the initiating VHF radio must acknowledge each received DSC position report received. Should multiple VHF radios automatically respond to the position polling request, then the possibility exists that the initiating VHF radio may not be able simultaneously process each of them. In the worst case scenario, it may only be able process a single DSC response. This subject should be researched via the VHF manufacturer. However, should it simply be desired that any one of the auxiliary craft be able to issue a distress message, have the ship's VHF radio respond to the distress message, and have the ship's VHF radio transmit the DSC position report to the MFD, then this should indeed be possible. Any DSC position reports transmitted to the MFD will cause the MFD to generate a corresponding alert and then provide an option to plot the position of the sender as a waypoint (not to be confused with an AIS or MARPA target). Should it be desired to perform DSC position polling, then the DSC VHF radios operating on the auxiliary craft each be programmed with unique MMSIs. Alternatively, should it be desired to continuously monitor the position of multiple support craft, tenders, recreational craft, etc., then it would be necessary to equip each auxiliary craft with an AIS Class B transceiver, each of which will in turn have a unique MMSI. Finally, the software presently available for Raymarine MFDs does not currently feature ability to initiate a VHF call.
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04-04-17, 01:12 PM
Post: #3
RE: Multiple VHF's single MMSI Question
Chuck, thank you very much for your in depth response.

Please allow me to further clarify my question..... Tthe following USCG page,
https://www.navcen.uscg.gov/?pageName=mtMmsi States: In the interim, VHF handhelds used in the United States should use the MMSI assigned to the ship to which the handheld is primarily associated, even if another radio on that ship uses the same MMSI.

If I purchase a handheld VHF with DSC features that uses the same MMSI as primary ship and if the handheld is activated by a MOB. Assuming the receiving VHF can handle the duplicated MMSI, will the MDF display the location of the handheld that uses the same MMSI as the receiving VHF.

As you noted, I will also reach out the the VHF Manufacturer.

Thanks
Jon
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04-04-17, 01:43 PM
Post: #4
RE: Multiple VHF's single MMSI Question
Jon,

The MFD will make no distinction between the own vessel's radio and an handheld radio using the same MMSI. Should the vessel's VHF radio to which the MFD has been interfaced transmit NMEA 0183 sentences or NMEA 2000 PGNs to the MFD which contain a DSC position report, then the MFD will alert the user of having received such data and will provide an option to plot a waypoint at the position included within the DSC position report.
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04-05-17, 01:44 PM
Post: #5
RE: Multiple VHF's single MMSI Question
Perfect! Thank You! -Jon
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04-05-17, 01:58 PM
Post: #6
RE: Multiple VHF's single MMSI Question
I thought I would add the following response I received from Standard Horizon.

"if you send out a distress on the HX870 your GX215W will ignore DSC call as it has the same MMSI number."
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04-05-17, 02:01 PM (This post was last modified: 04-06-17 08:30 AM by Chuck - Raymarine - Moderator.)
Post: #7
RE: Multiple VHF's single MMSI Question
Noted and you're welcome.
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