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Ask Sail: VHS/GPS Interface Woes

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Ben Hall of Chicago, Illinois, asks:

I just bought a new 25-watt VHF radio with a built-in AIS receiver. I began seeing AIS targets right off the bat, but got no graphic or numerical information as to their location in relation to me. A call to the manufacturer revealed that my new radio needs to know where it is before it can display data on where local targets are in relation to my position. Makes sense, but neither the VHF nor my current fixed-mount GPS have a common magic plug to export GPS output to the radio. Is there no standard plug for making these connections?

Gordon West Replies:
“There is no agreed industry-wide standard wiring interface,” comments the Radio Technical Commission for Maritime Services to the National Marine Electronics Association, so I  recommend that you turn the job over to a professional NMEA marine electronics installer. You could also dig out both instruction manuals and they will show you the NMEA output data wires from the GPS to the NMEA input on the VHF. In NMEA wiring terminology the GPS is dubbed “talker” and the marine VHF is called “listener.”

The Coast Guard wonders why the majority of DSC distress alerts it now receives through its Rescue 21 system come with no imbedded GPS data. No mystery here. Until the NMEA can get all manufacturers to make this important VHF/GPS connection via a simple common plug, we will continue to see thousands of VHF transceivers that don’t send position info with a DSC data burst.

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