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    Re: Test your magnetic compass.
    From: George Brandenburg
    Date: 2012 Nov 20, 12:20 -0800

    Just an amusing sidelight. On our sailboat I wanted to position my Garmin chart plotter (model 546) a little lower, which brought it closer to the compass housing. However, I had noticed in an appendix to the Garmin manual that it said it shouldn't be mounted within 50cm of a magnetic compass. When I tested this, I saw significant compass deviations when the GPS was brought near, and this was the case whether or not the GPS was turned on! I had been expecting to see a much smaller effect, if any, from the active GPS circuitry, but was quite amazed and disappointed that the device was intrinsically magnetic!

    I googled it to find out what others had discovered, and it turns out the problem is amazingly simple, and if I may say so, stupid. There is a small slot for an SD card on the face of the GPS, and it has a little watertight door over it that is held closed by, you guessed it, a permanent magnet. What were they thinking!!

    George B
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