Re: GPS Velocity Measurement

Gordon (hlg@pacbell.net)
Mon, 23 Nov 1998 11:03:23 -0800


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Good point. MinnKota even supplied a fused wire to connect from the
negative terminal to something that is in contact with the water, this to
reduce or eliminate interference with electronics, such as depthfinders.
The iron centerboard is the logical place to connect it. The GPS wasn't
generally erratic though, except for the speed readings. It was quite
steady and regular in counting down the distance to the waypoint and
reading out the heading to the waypoint. But I think I will add the ground
to the centerboard.

Now that you mention it, I remember the GPS was being held within a couple
of feet of the motor cables at the time the speed readings were being
taken. Since the compass was also nearby, I had twisted the pos and neg
cables around each other a couple of times in that area, but I don't know
how effective that was. That should reduce the magnetic field but probably
wouldn't have any effect on the pulse interference.

Regards,
Harry

>Check if the problem is still present while under sail alone...
>
>You could have pulsing interference (EMPI) from electric motor. I understand
>most electric motors also transmit an electromagnetic pulse that may interfere
>with electronics... That's why cars use resistor plugs to keep noise out of
>car radios...
>
>If this is problem... One possible cure is moving the GPS fwd away from
>motor...

>Best
>One Hand Lou