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			Phil,
 Although my instruments are ST50, I am using the Raymarine Multiplexer which
 has NMEA to Seatalk and also a proper RS232 interface.
 
 GPS (nmea), instruments (seatalk) all show up on my notebook as well as the
 GPS position data on my  DSC radio. GPS data is also transmitted across the
 multiplexor to the autohelm (but I believe the GPS position resolution is 2
 decimal places instead of 3 on the seatalk side of things). I used the free
 Seaclear software to prove that all data is being received on the PC.
 
 Regards,
 
 Stewart
 "Phil Stanton"  wrote in message
 ...
 Sorry to post this again, but I have failed to resolve the problem, and
 have more clues.
 
 I have a Raymarine ST60 Multi and want to get NMEA data (Wind & Depth)
 into the 9 pin serial port on my laptop. If the laptop is not connected to
 anything at all (including power supplies) this works fine. If I connect
 it
 to the boats 12v supply via a cigarette type laptop power supply, or an
 inverter using the normal laptop power lead I get nothing.
 Equally if I connect the USB port via a Serial to USB lead to the GPS and
 AIS input I immediately loose the NMEA input.
 
 Kees suggested using an optocoupler which I bought (not cheap) from Active
 research which looked as if it should do the job. They are boat people and
 supplied me with a 2 way adapter cable for NMEA In and out to serial plug.
 Just occasionally with the computer not connected to either external power
 supplies or to any other equipment a got a little garbled NMEA through.
 
 I have replicated everything on my son's laptop, a totally different make
 so I think we can eliminate the computers. I can connect the laptop
 through a cigarette type laptop power supply to an external car battery
 and again no problem. If I connect the negative of this battery to the
 negative of the ship's battery I immediately loose the signal.
 If, with the computer isolated and the NEMA going in correctly via the
 serial port I connect the optocoupler input across the NEMA out terminals
 I again loose the signal. Its as if there isn't enough power in the NEMA
 signal to power anything.
 
 2 other things. If I put a GPS signal into the serial port there are no
 problems even when the laptop is connected to the ships power supply again
 confirming that the laptops seem OK and that HyperTerminal is configured
 correctly.
 Along with the equipment mentioned above, I also have a Raymarine S1G
 course computer.
 
 Has anyone any further ideas
 
 Thanks,
 
 Phil
 
 
 
 
 
 
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