Re: Electronics

Bob Larkin

A couple more thoughts.  The John A antenna would be acceptable using 2 ground plane elements instead of 4, making it 2D instead of 3D.  That often can be tucked into the wall of a boat as high as practical.  For AIS, it does what is needed, almost always.  I have used essentially that antenna for AIS for years and years, resulting in stories, like the speck on the horizon that, on the AIS, is 90,000 tons coming at 19 kts on a collision course.  Good info to have!!

The splitter is a slight misnomer.  Because of the proximity of AIS and other marine VHF, it needs to also have a relay to disconnect the AIS when the VHF transmitter is on.  This needs circuitry and 12V power.  The real issue is that you are putting all that hardware un-reliability into the path of the marine VHF antenna.  That being one of our major safety items.  A less major issue is that the Glomex includes a 15-dB preamp to make up for the splitter loss.   The 15-dB is way too much and will create potential VHF radio overload problems that Icom and Standard worked hard to not have.  A separate antenna dodges both of these issues.


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