Sunday, 18 January 2015

Moved Aboard and Extreme AIS Range

Hi everyone,
Last weekend we moved back aboard Zen Again.  It's good to be back.  It was an extremely busy week but the gear we brought aboard is now either stowed or disposed of.

During the week we installed a couple of items...

  • 300W inverter
  • VHF antenna splitter

The inverter replaces the 100W portable inverters we had been using previously, and which are getting a bit old - their fans are now quite noisy.  The new inverter is a Sinergex PureSine300.  It is performing well and so far none of our loads have caused its fan to start at all.  A big improvement.

The antenna splitter allows our Vesper XB8000 AIS transponder to access our masthead antenna.  Previously it was using the emergency antenna on the pushpit which is much lower so gave a much shorter range.  Even with a masthead antenna the normal range is around 50nm.  Tests today showed that we're getting extremely long ranges, which _must_ be due to unusual propagation conditions.  We can see targets 700nm away!

700nm AIS range
Weather Map
Is the High producing a temperature inversion and VHF ducting?
Just to be clear - the above AIS picture is directly from our class B AIS unit and displayed on the OpenCPN chartplotter software.  No satellite AIS here!

Interestingly our Garmin chartplotter, which receives its AIS data from a separate AIS receiver, blanks out AIS targets when zoomed out a long way.  However, by zooming in just enough to keep the targets on-screen and panning away from our current position we can see the same targets shown in OpenCPN.

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