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966Re: [aismon] GME GX558A VHF Radio setup

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  • Mark Phillips
    Sep 27 9:54 AM
      Sounds like whistles? Shouldn't do. To a human ear 9600bd GMSK data sounds almost like white noise and therfore is almost indistinguishable on cheap radio speaker.

      How far are you from your intended monitoring area? In reality you won't get anything useful more than about 10 miles from the port. If you are on higher ground that may improve. I'm 40 miles from my nearest port and I'm 1000 feet up. Even then I only get a few posits a day and most of them are over night from the local Coast Guard station on Staten Island.

      Things to check .....

      1) If you have an audio meter in your software make sure that you only drive it to around 3/4 of it's range. This should prevent it from becoming overloaded.
      2) Try different software
      3) Raise your antenna higher and get it outside if possible (an indoor antenna really doesn't work too well)
      4) Do a plot of your terrain. NASA did a radar sweep of the planet from the shuttle a while back. Their data is online. You can see what the terrain looks like between you and the target. Large hills or buildings could make things tough no matter how close you are. http://www.pizon.org/radio-mobile-tutorial/rf-coverage-plot.html
      5) Are you taking the feed from your radio in the correct manner. It will not work if you connect up to the speaker line. You'll need direct access to radio's discriminator output otherwise the filters in the radio's audio amplifier will chop your signal up.

      Let us know how you get on!



      On Fri, Sep 27, 2013 at 9:13 AM, Pedro <ct1ekd@...> wrote:

      What software you are using for RX AIS?
      When coming the AIS signals it sound like a whisthles. Do you ear it?
      Pedro - CT1EKD
      ----- Original Message -----
      Sent: Friday, September 27, 2013 2:26 AM
      Subject: [aismon] GME GX558A VHF Radio setup


      I have modified a GME GX558A VHF Radio and connected to Windows XP laptop.

      I can hear the static sound coming thru to the laptop and the AISMON screen shows full level sound but I don't see any decoding happening - No Syncs.

      Does this mean something is not working or just no ships in range.


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